The Atrix is a pretty great phone by itself - two 1GHz cores and 1GB of RAM makes things speedy - but it's even more useful when you dock it into their laptop for heavy duty computering.
There are two ways to dock the phone into desktop mode, either by the HD Dock, which has three USB ports and lets you use it as a mini nettop, or into their custom laptop, which has a screen, keyboard and trackpad built in. Both ways can charge your phone, and the laptop has eight hours of battery life (provided you start with both devices charged all the way).
Once you get started, you get your standard phone features, of course, in a smaller window (that can be full-screened), but you also get a desktop version of Firefox in order to do more "serious" work. And yes, it has Flash 10.1 support.
Firefox runs speedy, loading Giz at a fairly reasonable rate, especially for a phone. It handed 720p YouTube videos fine and plays back its own 720p on-board media even smoother. They aren't thinking of adding more apps other than Firefox, keeping this a web-centric laptop, kind of like the Chrome OS netbook. So it's like a Firefox OS netbook.
The trackpad, if this is the final version, is a bit finicky, but the keyboard is solid, if slightly small and chicklety. Its screen is definitely netbook-esque, because the viewing angle isn't fantastic, but decent enough for something that's powered by a phone.
What's cool is that you have access to the phone UI as well, from the laptop, meaning that you can do everything you can on the phone but on a larger screen. That means playing games, making calls or anything else. And, of course, the phone charges while plugged in.
Speaking of the phone, the Atrix feels solid. Holding it reminds me of a Samsung Galaxy phone if they had only made the back less plasticky. It's light. And has a big screen. If being able to power a desktop version of Firefox is any indication, it's also a very fast Android experience.
Based on the hands on, the Atrix + dock/laptop dock combination is a pretty strong mobile computer. It's cloud-based, like the Google Chrome OS netbook, but has the benefit of being Android too. Very strange that Motorola is the one to bring this out, and also very strange that they're using Firefox instead of Chrome—which could theoretically get some kind of additional Google/Chrome functionality going.
I could see Google rigging up this functionality for all Android phones in the future, turning all Android phones into a potential Chrome OS computer. Wouldn't that be awesome?