I've been using watchOS's custom complications since they debuted in 2015, and I don't know how I ever used 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? They're, quite simply, the best.
Beyond an initial tap or raise to wake, 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.
Complications are perfect for the no-touch lifestyle. For travelers, seeing airline, train, and traffic information will prove life-changing for getting around without your iPhone. Add in a wake on wrist raise, and you'll 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 number 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 practically require multiple saved watch faces. I've already made one for weather-checking, one for traveling, one for to-dos, and one for goofing around.
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 fiancé, who so far has been pretty unenthused about the prospect of owning an Apple Watch, gave a start and a "Whoa, that's amazing" when I showed him the ETA complication and Time Travel.