After a week of living with the new Apple Watch Series 5, which goes on sale Sept. 20 for $399 (£399, AU$649), I can report that its always-on display delivers what I've wanted.The Apple Watch Series 5 It's an upgrade that was long overdue. I notice it a lot because now I can glance at the time when I'm typing. Or casually watching TV. Or driving. No more weird arm twists. And no more awkward comparisons to other always-on smartwatches, which include the Pebble, Amazfit Bip, Fitbit Versa 2, Samsung Galaxy Watch and Google Wear OS watches.

The always-on display is the key new feature in the Apple Watch Series 5.

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The other main upgrades are:

• A compass (magnetometer), which points you in the right direction when navigating with maps -- the iPhone has had one since the 3GS
• An international SOS trigger on cellular watches (no cellular contract needed)
• New premium (more expensive) finishes in titanium and ceramic

That's it. If you're not interested in any of these features, you can now get last year's Apple Watch Series 4 on clearance from plenty of retailers. (Right now savings seem to be about $50, but other deals could pop up over the holidays.) If you don't need ECG or the Series 4's larger 40 or 44mm display, Apple is continuing to sell the 38mm and 42mm Series 3 at the new official price of $199, which is basically what the watch's sale price was for most of the last year.

Read: 13 Apple Watch bands to get on Amazon  

All that said, the new display is a killer feature. I've been wearing an aluminum Apple Watch Series 5, and I fell in love with the always-on addition. It's now weird to look at the older models without it. But it's not always what you might think it is.

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I'm now using the Apple Watch more like a normal watch. And I keep thinking about all the people everywhere with Apple Watches on, showing blank dark screens. That's eventually going to change. Interesting watch faces will show up. Maybe ones that match bands.

Apple's new watch faces in the company's newest version of its watch software, WatchOS 6, are great, and there are dozens of watch faces now (34) with hundreds of variations. A solar dial face shows sunset and sunrise, with room for adding other bits of info like the weather or the date. Fresh information-rich watch faces such as Meridian and Modular Compact offer new mixes of shortcuts to apps. Download WatchOS 6 before you get a new Apple Watch, because its added features, which include podcasts and an ambient noise meter, could make your old watch feel new.

But still, even with these options, I find myself getting bored and looking for novelty. I'd like a watch face store for third-party developers to add unique designs, and that still hasn't arrived. The always-on feature further cements that desire. Maybe this will pave the way for Apple to allow third-party watch faces. Perhaps a curated collection from well-known designers to start? I'd buy a few.

Apple's making the always-on display work via new OLED display technology that slows and dims the display, freezing animations but offering up that always-on readout. One side benefit: The screen autoadjusts better in low light, like in movie theaters. It'll be interesting to see if this display tech ends up in other devices, including future iPhones -- which a lot of people still use as their main device for telling time. (Just for comparison, Samsung first launched an always-on display feature in its phones with the Galaxy S7 in 2016.)

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Here are some quick facts about the Apple Watch's always-on display:

• It won't affect battery life, but turning it off could increase battery. Apple promises 18 hours of battery life with always-on enabled by default. The new OLED display cycles down its refresh rate and the display lowers its brightness and reduces animations. So far, I've been getting roughly a day and a half. You could turn off always-on, and I'm testing that next to see how much better the battery life could be.
• It's only always-on for watch faces and the Workout app. Apple didn't allow other apps to stay always-on. Which means, when they're open, after a few seconds they'll disappear and a small generic digital watch face will pop up. If you had a dream of having anything on the watch stay always-on, you're out of luck. This can be helpful, though, if you have sensitive info on your watch. Turning it away will cloud it from view, like a privacy screen.
• Always-on only works on your wrist. The watch waits to sense skin contact before triggering always-on. When it's off your wrist (or charging) the display still turns off.

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• Every watch face has an ambient, dimmed always-on mode that kicks in. Much like Samsung or Wear OS watch faces, Apple's transform in the ambient always-on state. Moving second hands disappear. Background colors tend to fade to black or dim. Readouts shrink a bit. Some watch faces just look dimmed while others take on a second cool identity. Some are just boring analog watch hands.
• The watch needs to "wake up" before swiping, which takes a half second. You might see the watch face and want to swipe up a new one, or peek at notifications. But the always-on display needs to activate from sleep. Tapping wakes it up. It's a small delay, but be prepared.
• Active complications, like the new compass or noise levels, go dark. These things still need a wrist-turn to waken.