I'll +1 the magic mouse idea.
It's nice and flat so it fits in my laptop's case well for portability. It's so useful even without the aftermarket drivers that I find I really try to avoid using my old mouse (basic logitech mouse). I love the inertia scrolling and two finger forward and backward swipes.
Did have some aftermarket driver (not BTT, haven't really played iwth that one yet) but decided that it was more frustrating to use that way (so little space on the mouse it was easy to accidentally be hitting it with one more finger than you meant and have it do the wrong thing. Not sure if BTT addresses this by allowing you to appoint edges as not counting).
Of course, now that I have my MBP with the glass trackpad I don't really need to take my mouse with me (my old macbook had the old style trackpad with click button. I loved my Magic mouse so much I'd take it with me over using that). But when I have my MBP in desktop mode I still use my magic mouse over my other one.