I've been using it a couple of days now so here is a mini review:
1. There aren't many apps available for it yet but, some of the ones that are available are pretty good, such as Endomondo Sports Tracker, Music Player, Phone Battery Level Widget, Mode Changer (Changes to silent, vibrate, normal), call handling, calendar notifications.
2. Everything so far is working fine with the One X. When I spoke to Sony at mobile world congress they said some things might not be compatible with other phone makes but, so far so good.
3. It loses connection to the phone rarely, the only times it does is when you say fold you arms and cover the watch, and while your phone is in your back pocket, the signal obviously get's lost through your body mass, and no I'm not fat! I was walking around the house with it on with my phone kept in one room and it worked great.
4. The screen can be switched on by either pressing the button on the side or by double tapping the screen, however, I think the screen timeout delay is a little short, I would have liked a few more seconds added on and you can't change this in the settings currently.
5. The LiveWare app is pretty easy to use, you need to install this on your phone first before you can install apps on the watch. With this app you can enable/disable apps/widgets, you can also re-arrange the position of these on the watch screen. You can also adjust settings for certain apps.
6. The strap that comes with the watch is pretty comfy, I hardly know the phone is on my wrist after a while, it's very light.
7. The battery has only been charged once and it lasted up until today after the first charge so, about 48 hours so far and it has had quite a bit of use.
8. The screen is very sensitive and there is not much lag when using apps that need to access the phone, in fact it is a lot quicker than I was expecting, it's quite a seamless experience. A higher resolution screen would have been nice but I'll expect that in the next version, and maybe a bit bigger with a smaller bezel but, in general it looks quite smart on the wrist, especially at night as the display lights up really well, much better than a normal watch with dodgy backlights!