I've had mine for a month or so and I've done about 10 dives with it. Some pretty deep and long ones, too.
The display really is great, as is the tap interface. Its very intuitive. The only thing I needed the manual for was the stopwatch shortcut. The color options make it very easy to pick out what information you want at a glance. I was scootering side by side with my buddy in a cave on Sunday, and I could read his unit just as easy as I could read mine. Even with the lowest brightness setting, its CLEARLY visible in shallow open water, too.
There are some little issues with the software, but nothing major. Mine does lose a few minutes a day, however. I was told that will be fixed in the next update. No problems with it not turning on at 4ft, however.
The unit is surprisingly small. From the pictures and video I've seen, I expected a brick on my arm. In reality, its the same size as my Uwatec bottom timer. The back side is a bit taller, but the front side is substantially shorter.
Overall, I'm more than satisfied with it. I wanted a simple, functional bottom timer that I could easily see and use on cave dives. The Xen has certainly delivered. The additional features are really icing on the cake.