I absolutely love its geekiness. I'm running it with a stock Nexus 1 on 2.2.1. Yes It does disconnect all the time and I spend quite a lot of time turning it off and on again, re-pairing the bluetooth and generally willing it into life. But, I'll definitely knock a couple of apps up for it in the hope that SonyEricsson make a second generation device with a higher res screen, full touch support and a longer battery life. Some say the battery life is pathetic, but that is an understatement, a watch that doesn't get through half a day is crazy.
So far the best use for it is remote controlling the music players, i've had no problem with the built in Music remote control and my Nexus 1. It supports play/pause, volume control, next/previous track. The Where Am I plugin is ok, brings up a map of your current location on the LiveView. The GMail and SMS plugins don't seem particularly reliable, but I'll keep persisting.