I've been using a MS IntelliMouse Explorer 3.0 at work and home for the past year or so and I've really liked it.
I recently bought a Logitech MX310 to use on my T221 workstation at work. This system has been a real joy and pain to work with, it's a 23 inch 9.2 mega pixel LCD @ 204DPI so it looks wonderful and it's a joy to look at, but because of the high resolution you have to move the mouse repeatedly to get to the other side of the monitor. So I figured I'd try the 800DPI Logitech mouse and see if that helped.
It did, in so far as I can now move from edge to edge in a single hand movement but it's impossible to aim accurately at that speed. I tinkered with the mouse speed settings for days hoping to find the magic combination that would be acceptable, but no luck. So I went back to the MS mouse, I prefered it's feel better anyway. The Logitech was too high in the back of the mouse for my liking anyway.
Maybe I should get a digitizer again... I used a Calcomp Drawingboard III for years when I did AutoCAD work and I loved it's 16 button cordless puck, I think I still have one in in the attic somewhere...
The way a digitizer works as an absolute coordinate system is very intutive and once you use one for a while you'll be hooked on the great control it gives.
Say that reminds me, you can get a mouse for Wacoms... I have a Wacom hooked up here...
Off to find a 4D mouse on eBay for my Wacom tablet...