Bought my first Intellimouse Explorer 3 several years ago and now have three, one for each of my computers. This latest purchase was to replace my first one, which sadly had to be put to rest when the left button developed a mind of it's own, but it had seen many years of hard service.
I have nothing but praise for this mouse, as it is easy to use and set up, is very comfortable in use, and my three have been very reliable. Some reviewers complain of a "clunky" feel to the mouse wheel, which is correct when first used, but in my experience this soon "runs itself in", after which it is a pleasure to use. The programmable buttons allow it to be easily configured to suit the needs of most users.
I am a software developer and have been using computers since the 1960's, and have used many mice since they were first introduced, and in my opinion this is the very best.