I've been using trackballs for nearly 13 years now. 12 1/2 of those years I was using the logitech marble:

http://www.tigerdirect.com/applicati...3572&CatId=540

The last 6 months or so I've been using:

http://www.tigerdirect.com/applicati...3571&CatId=540

I definitely recommend finger ball over a thumb ball. Not sure how you thumbies do it, my fingers are way more accurate/responsive than my thumb, but I guess everyone has their different talents =) I switched to the new wireless one because not having a scroll wheel was killing me. A lot of software/games incorporate good functions with the scroll wheel now, and sometimes things you can ONLY do with it. It shouldnt take too long to get the hang of it, I'd say less than 2 weeks if you use it a lot.