Also new to Android, coming from BlackBerry.
Does this mean I'll be able to not use Motoblur and use Android how Google made it?
Actually, you could do that even if the Atrix was not rooted, by simply downloading a 100% free app from the Android Market. You have a few options, but the main two apps which do this are called "LauncherPro" and "ADW Launcher". Like I said, both are free to download. They replace your motoblur "home" in favor of what most people (though not all) think is a better way to organize things over motorola's ideas.
Rooting just means you are now a superuser who can delete the "bloatware" AT&T will have put on your phone when you receive it, like AT&T Navigator, etc, which take up space and clutter up your app list and everything. If you have Vista/Windows 7, it's kind of like being the Administrator rather than just a user, I guess.