Before I get to the negative, I'll focus on what I like about this dock...
First of all, it WORKS... it just does! My Xoom fits to the dock, it charges... I can plug speakers into the dock, and they work. In those terms, this Dock fulfils it's purpose perfectly.
The interchangeable tilt plates are a really nice touch, though the stock plate is made of superior material to all alternatives (with a lovely matte rubber feel to it). The alternative plates are made of a typical grade plastic, and at first I was concerned that they might scratch the casing of my beloved Xoom. However, so long as you're gentle when docking, I'm now confident this won't be an issue.
What most people don't know is that you can easily fit a Gel-case covered Xoom into the dock, simply by removing the interchangeable tilt plate. The docking fit in this situation is actually very nice, not exerting any unwanted stress on the connectors, or the Xoom.
Now for the unfortunate downsides:
1) This dock has no USB connector, so it's impossible to transfer data between the Xoom and your PC via a fast, reliable cabled connection when docked.
2) This dock has no HDMI connector, so it's impossible to connect your Xoom to a HD screen whilst docked. Personally I think it would've been clever of Motorola to provide a NORMAL HDMI output on the dock, which converts from the micro-HDMI port on the Xoom. This would have made the dock even more useful than just "somewhere to put your Xoom when it's charging".
3) Because the dock is very small (particularly in its width), the Xoom can rock horizontally when docked. Whilst I'm confident that this won't break the precious connectors, I can't help but fear that the Xoom could possibly fall out. True, it hasn't happened to me yet, but the lack of confidence it inspires is itself a problem.
The lack of these two fundamental features, and the horizontal rocking issue reduce this dock from 5 stars, to 3.
Of course, I haven't found a better altnerative to the official dock, so I would still strongly suggest you buy it. It's practical to charge in a docked situation, and (if I'm absolutely honest), it looks really nice.