I also use Logitech trackballs at work, at home, and with my music system. I love them. I can't see what any other higher priced device would buy me. Some of mine have the large ball on the right and some have the smaller ball on the left. I love them both.
I also use ergonomic keyboards. They take a few days to get used to but after that they are so much less stressful to your hands than a standard keyboard.
I currently use the Logitech Trackman Wheel both at work and at home. But I've been having some wrist pain lately, so I'm considering getting something else to break the monotony. Possibly a Wacom tablet or a Contour RollerMouse Pro.
Right now I'm only using a Wacom 6x8 at my office job. I used to use a 4x5 at home with Cakewalk & GS2.5, but it was serial. When I went to two computers and a USB KVM, I could only use the tablet on one PC, and I slowly went away from using it. Now it's disconnected. Maybe I'll ask for a USB tablet for xmas.
Unless you're doing detailed artwork, I recommend the 4x5. I've never felt it to have too little resolution. I prefer that I don't have to move my hand so far to go from corner to corner with the smaller tablet.
Logitech Laser mouse. I like the weight; not too flimsy, it is extremely accurate and has quite a few programmable buttons which means that I can do things using mouse only, rather than having to hold down a key and click.