1) it's a little strange to be wearing a watch again.
2) the apps screen gets full really really fast
3) I want to write complications for it. Complications are the elements that can be configured in watch faces. A quick google search has not turned up any information on creating them.
4) It was obvious that the watch was going to be a relatively simple i/o device attached to my phone. Brief experience bears that out -- with the exception of the watch face and complications (some of which DO depend upon the iPhone -- Weather, for instance) -- it's a new interface into existing apps on your iPhone.
As such, it creates a new category of interactions which used to be folded into your phone -- extremely brief ones for which you might have carried your phone in your hand (e.g., moving to the next song or changing the volume on your music -- exactly what buttons on your headphones or cable were intended to do) -- like incessantly checking the time, or a countdown timer you have in place.
So I'm not quite sure that I like the idea of games on the watch. If you are sufficiently engaged in something to interact with it constantly, why not use your phone, which has a bigger screen and better UX? The only game type I can see working on the watch is something where you make a very simple decision every few minutes or so. Definitely NOT highly interactive systems.
5) Oddly, the watch is more intrusive than the phone for interacting, because it absolutely requires two hands. There are a lot of things I can do on the iPhone with a single hand (the previously mentioned music manipulations, simple short texts or typing with one thumb, swiping, etc.) but I have to have my phone out and in one hand to do it. The watch, which doesn't need to be taken out or put away, must be manipulated with the opposite hand. It sounds small but it it weighing heavily right now -- partly because in each case the primary use hand is my right hand. If i'm holding the phone to do one handed manipulations, it's in the right hand. If I'm manipulating the watch in any way other than just flipping my wrist to the see currently displayed glance or app, I'm doing it with the right hand. I assume that lefties will act correspondingly using the left hand.
Anyway, those are the first thoughts. More later, I imagine.