yeah its brush based and really easy to get into - far easier than ZB from a basic level but then again it doesnt have half the tools. I know Mudbox 2 was on the cards this year and would probably be including 3D painting and some other nifty additions to bring it more towards the likes of ZB whilst still being sufficiently different.
Here's hoping that Autodesk really push it and start throwing lots more development at it. It'd be nice to see the displacement mapping features fully integrated with maya and 3ds max as it can be a bit tricky to find nice settings.
I think a standalone would probably be better for now but there wouldnt be anything wrong with integrating it directly into the maya/max interface for some seriously good modelling capabilities.
I read the mudbox forums a lot and you get the usual gripes about autodesk possibly screwing it up but I think that it'll develop a lot faster for the better now