http://www.logitech.com/index.cfm/products/details/US/EN,CRID=6,CONTENTID=5002
Funny, I encounter those trackballs frequently at customer sites and regard
them as absolutely the worst possible pointing device! They are slow,
inaccurate and hurt the thumb after a short while.
I'm right handed but found it best to use the mouse with the left hand. The
left hand is faster and more accurate than the right that's why so many top
tennis players are left handed. I've been using the PC since 1986 for up to
12 hours a day this way and never had a single problem with my hands or
shoulders. I've always preferred a big desk and rest my elbows or forearms
on it while working. I absolutely hate those "workstations" type of
furniture with sliding keyboard trays and multilevel surfaces for keyboard,
mouse and monitor. They certainly give your hand and shoulders problems
because you can't rest your elbows or forehands anywhere.