Well, there's good news and not so good. The not so good news is that some systems, regardless of power, just won't run MB at the moment. The team is supposed to be looking into it but I don't know how that's going.

Mudbox takes some getting used too, that's for sure. If it's any consolation, I didn't start really "getting it" until the last day of my 15 day trial, so it doesn't surprise me that you're a bit confused off the start.  Stick with it though. It is much easier to get things done in MudBox than ZBrush in my opinion but it's not as jump in and play as it could have been.   The best advice I can give is build up your displacement. Don't subdivide to the max and then start displacing because you usually end up with a lumpy mess. Refine as you subdivide, using the smooth tool along with the other tools so that the bumps and strokes you place on the mesh can  blend together better. Of the 5 or so programs I've tried that can do displacement painting, I've found the Silo 2 Beta the easiest to just jump in and play, which is unfortunate, since the poly count is limited to about 2 million per object...of course, if you break your model up into several smaller objects, we're talking 2 million for each part. :) That's my personal opinion though and should be taken as such, since just like it says above, no one can tell ya what works for you.

Having said all that, MB is just easier to get into that ZB...or at least, a bit less stressfull on a person's memory and eyes.  Post some shots of what you're doing Tom, maybe I can point out where things could be done differently and how it can be. I don't have MB any longer but the principles are the same regardless of programs. Only interface and workflow differ.