I have Series 0, and it's incredibly slow – to the point that it's usually faster to pull my phone out. Did you notice a big speed change with Series 2 that made it more useable?
My wife and I have a Series 2 and we haven't had any problems with lag. I didn't have a Series 0 though, so I can't directly compare. However, for most of the things that I do with the watch it is decently responsive and definitely not frustrating.
Also, it seems to actually have about 2 days of battery life; for example, I've been wearing mine now since 7am and I'm at 67% battery.
[doublepost=1485997721][/doublepost]Wife and I are very pleased with the watch overall. I think she'd be happier if the battery life was one week. I charge at night (and I wouldn't want to sleep with the watch on anyways) so battery life is not a big deal for me.
Some dumb things don't work..for example you can use the "find my friends" app to find friends but you can't ask Siri on your watch (I'm guessing they'll fix that sooner than later).
When I'm in my car sometimes it's easier for me to control the music from my watch (like selecting a playlist) instead of using the head unit or phone. Maybe if I had a CarPlay head unit that wouldn't be the case but for now it's convenient to have the watch.
I also like knowing when messages come in without having to grab my phone.
Surprising enough, my wife and I use the watch to find our phones fairly often as well.
My personal preference about future versions: I'd prefer a thinner watch just because I like the thinner look. I know some people like bulky watches but I'm not one of them. Knowing how Apple is, I suspect that future versions will be thinner.
Also, I know some people with the Fitbit "blaze" watch and I think it is super ugly and cheap looking. I can't believe so many people have it...it's really not that much cheaper than the Apple Watch. One thing I have noticed is that people that wear the Fitbit generally don't have much style/fashion and are cheap so I guess it all makes sense.