Editors' note: Updated April 27, 2017 with some verdicts and photo samples based on a few hours shooting with the A9.

Full-frame cameras for pro sports and wildlife photographers are the last bastion where dSLRs still rule. But the Sony A9 looks like it has the chops, if not to bring their reign to an end, to at least make significant inroads into the territory held by the Canon EOS-1D and Nikon D5 series models. In addition to a maximum continuous-shooting speed of 20 frames per second matched by a 693-point phase-detection autofocus system, the A9 brings in-body image stabilization, something those dSLRs lack.

Preorders start Friday, with shipments expected in May (US) and June (Europe). The body will cost $4,500, which may sound like a lot but is actually pretty reasonable. And it's effectively a lot more expensive in the UK and Australia, where it will be £4,500 and AU$7,000.

There's a lot to unpack here.

As I see it, the A9 offers these advantages over a traditional dSLR:

Size: This one's a no-brainer: given similar capabilities and quality, smaller is better. The E-mount lenses are substantially more compact that those for full-frame dSLRs, making the whole kit and caboodle much more manageable.

Verdict: Oh yeah. My back usually aches after a couple of hours hoisting something like the D5. I could have shot with the A9 and the 70-200 mm GM lens all day.

Speed: For action photography, frame rate is important but so are autofocus and autoexposure speed and accuracy, as is the speed with which the camera can write to the card. Because it uses an electronic rather than a mechanical shutter, Sony's 20 fps outpaces its dSLR competitors. Typically Sony cameras have awful write times, and I think the A9's crammed full of buffer memory so that you don't notice. It can also do in-camera slow or fast motion; not nearly as extreme as the RX series, but more than the dSLRs.

Verdict: Mixed. The ability to do even 120 fps slow motion in HD is great and looks good. The autofocus tracking works really well for the most part, though it's really frustrating when it lags just a little. If you're going to rely on it, you need to figure out when it's going to let you down and compensate. And the autoexposure system needs to get a boost to sync up better with the autofocus, such as with some sort of tracking zone AE. Finally, I was right about the write speed. While you don't notice most of the time, if you shoot a longish burst, especially of raw or raw + JPEG and then try to switch to video it simply can't dump the buffer to the card fast enough. And if you're splitting the JPEGs and raws to the different cards the slow write speed of one slot holds you back.

Price: The A9's body costs significantly less than the dSLRs.

Video: Shooting video with mirrorless cameras -- especially the Sonys -- is such a better experience than using a dSLR. You have live view with the ability to see color and exposure in the viewfinder; you can actually use the viewfinder for video!

Verdict: Mixed. Unsurprisingly, shooting video with the A9 is a really great experience. But I was surprised that the A9 doesn't support Sony's Picture Profiles, its system for using custom gamma and colors, such as its own S-Log.

Mirrorlessness: Canon and Nikon go to a lot of effort to keep the mirror -- the "reflex" in dSLR -- from thwacking up your photos. Mirror movement, typically the bounceback, causes vibrations. It also makes noise, and using the quiet settings on a dSLR frequently requires a slowdown so the mirror mechanism can gently return to position. It also contributes to the durability; one less set of moving parts to worry about. Sony didn't provide any shutter durability specs, but it's likely at least as good as the lower-end models, which is 500,000 cycles. Since mirrorless models can rely more on electronic shutter, the mechanical one doesn't wear out nearly as fast.

Verdict: The camera is so quiet that several people actually turned the shutter noise on to be able to tell it was capturing! When I started to use it, I noticed a flickering box around the subject in continuous-shooting mode. Turns out, that's the indicator which tells you it's working.

Sensor-shift stabilization: Also a no-brainer. It works with any lens, obviating the need for extra-cost stabilization in lenses.

Verdict: Wow. Even at fast shutter speeds I tend to get some shake when I'm trying to override my instinct to follow the subject with the camera rather than letting the autofocus do it for me. I don't think I saw any stabilization problems in my photos.

But the A9 has some drawbacks as well:

Price: It costs a lot less than its dSLR buddies, at least until you start loading it up with the grips and batteries to bring it up to par.

Battery life: Mirrorless cameras typically have awful battery life, and the A7 series' is among the worst. Sony's made a big deal about the battery in the A9, which isn't new but is more than double the capacity of the A7x's. Those viewfinders suck a lot of juice. But if you look at the rating for the A9, that doubling of power only translates into approximately 30 percent more shots with the viewfinder, to a subpar total of 480 shots. Even without the viewfinder it's only 650 shots.

At 20 fps, you'll go through that in no time. It's true that your mileage varies significantly when it comes to battery life, but it's just not promising. You can buy the new battery grip, which holds two batteries and in theory brings your viewfinder-shooting duration to a more reasonable 1,440. And as one of the members of its Sony Artisans program which the company trotted out for the announcement said, she's used to carrying a bunch of batteries around anyway.

Verdict: This was a terrific surprise. After more than 4,000 shots (with more than 3,000 raw + JPEG) and a handful of videos the battery dropped to only 70 percent.

Build quality: Canon and Nikon's bodies are built like tanks, with dust-and-weather sealing that's been honed over time. They feel like they could survive being kicked around like a soccer ball in a monsoon. The A9 has build and sealing that's a little better than the A7 series'. Good, but hardly in the same league.

Storage: The camera has dual card slots, which is essential, but only one of them supports fast UHS-II SD. Even if the camera doesn't fully utilize the fast cards to speed up shooting, you definitely want them for downloading. But never fear: It still supports Memory Stick.

Verdict: Ouch. As mentioned above, the slow card slot is a real problem. I filled up the fast card and was forced to rely on the other because I didn't have time to swap cards, and I really felt it.

Lenses: As this is Sony's first foray into pro E-mount territory, it doesn't have nearly as many fast supertelephoto options as other systems. Sony did announce a 100-400 mm G Master option in conjunction with the A9, however. You can certainly use other lenses with adapters, but they're big (see "defeats the purpose") and you take a speed hit when you use them.

There are also lots of unknowns for the moment:

Quality: This is the first stacked-CMOS version of a full-frame sensor, so we really don't know what to expect. Sony also won't say whether it has an optical low-pass filter on it or not.

Verdict: I was only able to look at the JPEGs -- the raw codec isn't available yet -- and only shot as high as ISO 6400, but as long as it's in focus, it looks quite good. As with most cameras, even a little motion or defocus drastically reduces sharpness as ISO sensitivity rises. But because it handles continuous-shooting so well, even if there were some slightly out-of-focus shots in a burst, there was usually one good one; that helps a lot with high ISO-sensitivity shooting. Nor did I see any noise in dark areas or loss of saturation.

Autofocus accuracy: There are myriad ways to configure the autofocus, and some produce significantly better results than others. Sony has the most faith in its lock-on group autofocus, but it's oddly more difficult to use with subjects moving quickly than traditional servo autofocus systems -- you have to center the group autofocus point over the area of interest and press a button to lock it in. That's a little harder to do with fast-moving subjects. And there's a little lag while it catches up with where it's supposed to be next. It remains to be seen whether the types of AF people want to use sync up with what's optimized.

Verdict: My mind hasn't changed about the AF lock implementation, but the zone autofocus works quite well and pretty far out to the edges of the frame. While it uses eye-recognition to supplement its ability to lock onto faces, for the most part it prefers to lock onto people's torsos -- a much bigger target -- and will jump to the next one it sees if your subject becomes obscured. Most of the time it jumps back, but not always. It handled different types of focus situations adeptly as well, including the subject crossing through the frame and coming straight toward me. It also locks on the appropriate subject fast.

I could go on, but I won't. Regardless of whether or not Sony manages to make a dent in the market share for pro cameras, it's definitely injecting a much-needed bit of competition to shake up the somewhat complacent two-party race in sports photography.