This mouse is amazing. I had one several years ago at my job. I went searching for it to use at home. It is terribly hard to find, which is sad because it is a GREAT mouse to use, especially if you already have some wrist pain or are trying to avoid ever getting it.

Keeps wrist upright; click with thumb

Need to replace batteries; no back button

I wish there were one size smaller. The 550 has a better surface and optical sensor than the 500, but the batteries need to replaced from time to time.

My hand is 3.5" across the palm and the Small size is still a bit too tall vertically for me; The wireless signal is not that strong, so it helps to be near the receiver; The batteries add weight

Takes a little getting used-to, but this little thing really works! In two days, my forearm strain totaly disappeared. I bought the wired version--no mechanical problems whatsoever. Very accurate.

Excellent! Takes a little bit of time to get used to it, but its amazing!

I have been using this 3M ergonomic mouse for past 3 weeks now and I am pretty impressed that the pain in my arm and wrist that has been there since 6 mos because of herniated disc in my neck has almost gone.

I was excited to find a 'joystick' mouse, to relieve my clicking-finger stress-even such a tiny movement repeated all day causes stress up to my shoulder. I hoped holding my hand in one place and moving it like a joystick would be different, but that's not how it works.

Ive been using this mouse for years. I write a great deal in my work, so this has saved my wrist. My only complaint is that they only seem to last less than a year before I have to replace. That kind of planned obsolescence isnt cool.

I purchased one for work and after a year or so I had to have one for home. I knit all the time and want to take care of my hands. Make sure you get the right size. I had the large one for a short time and the reach for the thumb was not natural.

Overall a good buy and reasonably priced

Easy to use and it really reduces muscle strain

Scrolling button seems to be a little temperamental

I use my mouse a lot and I was starting to get pains in my wrist and forearm. A friend of mine suggested a trackerball type mouse which I used for about three months, but it didn't solve the problem.

Easy to use and it really reduces muscle strain

Scrolling button seems to be a little temperamental