The main things for me are:
BT connection isn't stable. It drops constantly. Just pressing the right shoulder button normally re-connects and it goes for a while before it drops again. It's not a huge deal but it isn't working as intended.
Intermittent responsiveness of the buttons. I have to frequently re-start the device throughout the day (long press on the power button). This is usually because the BT connection has dropped. It's getting more stable the more I use it but it's not perfect.
Battery life - again, it gets better the more you use it but I've had anywhere from 3 hours to 7 hours without having to charge. Nowhere near the 2 days some people are reporting (I update twitter on a 15 min period and RSS hourly). I do play with it constantly so I'm not too worried about this.
Plugins - they seem to work intermittently. The gmail one is great when it works but it's hit and miss.
Phone - I should note that I've had no significant problems with either phone battery life or phone locking up since I started using it. That's not to say there aren't other software glitches since I've installed LiveView but nothing too annoying.
Music Player - this is so useful when you don't have to pull your phone out to change tracks etc... It's more convenient than you would imagine
Who's Calling - the only thing you can do is mute the call from the device but for me it's the fact that if my phone is in my pocket on vibrate/silent then I don't miss the call. Probably the most useful function so far for me
RSS - it's just cool reading news feeds on your watch. Period.
Where's my phone - does what it says on the tin
Plugins - there are some great possibilities but the ones now for me are: Contact Call [scroll through your contact list/groups and activate on phone] / Mode Plugin [change phone to vibrate/loud etc..] / Gmail [read mail on watch]
There are a few others others but these are the ones I use on a regular basis
All-in-all I like it a lot but it needs some work by not only SE but also developers to bring out the potential. There will be a firmware upgrade by SE service centre but I couldn't find any other details. Worth the money to mess about with. I use it everyday and will continue to do so as I genuinely like the device. I just hope that some interesting plugins come out or some firmware hacks maybe.
Edited by Moody Loner, 08 December 2010 - 02:04 PM.