I don't really want always-on, I just want it on every time I look at it. Which means: a) with less exaggerated movement to trigger it; and, b) with faster light-up time when it does trigger. Currently, on my Series 0, it's, hmm, perhaps something between a quarter and a half a second, that I'm dumbly staring at a dark/blank watch face, before it lights up with the current info. Yes, it might be faster on a Series 2, and yes, half a second isn't that long, but it's a tiny bit of annoyance every time I look at my watch.
I don't see them doing always-on with the current display tech, though I look forward to it arriving down the road. I suppose what they might be able to do now or soon, would be the just HH:MM display they use in low power mode, and move it around the face like an old-school dvd player screensaver to prevent burn-in. I'd actually be a little surprised if they haven't tried that in the lab. It'd be a bit inelegant, but useful.