After going through numerous mice in the last year or so, I've finally settled on a very nice and comfortable mouse that does not break the bank.  $60 CDN is a bit pricey, but this is something that I can rely on for comfort and ease of use for many months to come.  When the only negative about a product is just a minor flaw such as the feel of the left and right button clicking, then you've surely got a winner in your hand.  So if your PS/2 or USB mouse is on the fritz, then give the MS Intellimouse Optical a try...