The one thing we couldn't test in the watchOS 2 beta turns out to be the best feature of the bunch.
I've been using watchOS 2's custom complications for 48 hours and I already don't know how I've been using my Apple Watch without them. At a glance traffic information? Quick shortcuts to my tasks? Two taps to get directions for the hotel I'm staying at on Thursday? This is what I suspect Apple expected people to use Glances for, but for me, Glances didn't fit into my workflow. Third-party complications, however, do—and they do with aplomb.
Beyond an initial tap to wake (I don't use wrist raise due to its battery draining tendencies on the 38mm watch), I try to rarely touch my Apple Watch unless I'm actively using it. Currently, most of the passive information I get comes through notifications: checking to see if iMore is burning down while I'm at lunch, and the like.
Glances never fit into this equation for me because they required active input: If I wanted to check out a glance, it required tapping, swiping, and occasionally tapping again. It's too much work while trying to stay involved in a conversation or rushing around a terminal looking for the right train.
Complications, however, are perfect for the no-touch lifestyle. For travelers, airline, train, and traffic information will prove life-changing for getting around without your iPhone. Add in wake on wrist raise, and you never have to touch the watch at all—except maybe to change watch faces.
Enter the watch face explosion
I am very, very glad that Apple didn't limit the amount of clock faces you could create on the watch, because you're going to need them with third-party complications. I was already making different faces for different activities—a stopwatch-focused Modular for derby, a classy Utility for going out—but third-party complications are going to explode demand for multiple saved watch faces.
I've already made one for weather-checking, one for traveling, one for to-dos, and one for goofing around—and again, I haven't used complications for more than 48 hours yet. And I'm only using them more as time goes on.
Time Travel is the magic feature we didn't know we needed
Apple's new Time Travel feature looks incredibly gimmicky on stock complications. Calendar is kind of cool, if you have lots of appointments, but otherwise, not all that useful when paired with the stock apps.
Third-party complications change everything, and I'm not being hyperbolic when I say that. I did a literal jump for joy when I discovered that the ETA complication worked with Time Travel. Just spin the Digital Crown, and you can immediately figure out the best time to leave your house to avoid traffic or transit jams.
Weather apps are equally brilliant: Want to know if you're going to need a jacket or umbrella today? Twist the crown with an app like Carrot Weather enabled and you'll know in seconds.
Even the demonstration at WWDC was a perfect example of real-world greatness for Time Travel: Turn the crown forward to figure out if your electric car will be charged in time to leave for the airport.
Just the beginning
I've only tested 15 or so apps with third-party complications so far and I've already found several fantastic uses—I can't wait to see what developers have in store down the line. (Carrot Weather in particular is being extra smart about space by having their two complication sizes talk together in tandem, so you can get even more weather information on your watch if you have both enabled at the same time.) Even my boyfriend, who so far has been pretty unenthused about the prospect of owning an Apple Watch himself, gave a start and a "Whoa, that's amazing" when I showed him the ETA complication and Time Travel.
For me, it comes down to this: Even as a power user, I wasn't using a lot of third-party apps or glances. But 48 hours into watchOS 2, I want all of the third-party complications. All of them.
And my gut feeling is, this watchOS 2 feature is going to sell a whole lot of watches.