I have just purchased a Microsoft Explorer mouse.
Primarily this was to replace either the MS Natural 6000 I use at home, which is falling apart or the Trust mouse I use at work (who knows what model, just has a number on the bottom (14835) which is also falling apart and is eating AA batteries at an ever growing pace.
The Natural mouse is a great shape but I'm not great a sitting my hand on the mouse so isn't ideal and when I do consciously put it in the palm of my hand it is too small so I'm not using my finger tips to press the buttons. That said is an excellent mouse which is shown by its continuing relatively high price. The rubber coatings though are falling wearing off - just as they ae on my Trust mouse.
Enter the Explorer mouse. This is a great shape and sits in the palm of my hand much better than anything else I've tried before and supports my little finger fairly well so I'm encouraged to sit my hand on the mouse this time. It uses BlueTrack technology to improve tracking on various surfaces - the Natural mouse is ok on most surfaces but A4 paper defeats it - gives me a reason to keep my desk a least a little clear of junk. The trust is pretty Trustworthy all in all, can't say I've had any problem with tracking but reception can be a bit hit and miss. The Explorer mouse is better, much more positive, my beech effect, melamime worktop still throws it a little but not so much that I'm searching for another surface.
Issues? Build quality. As mice go this doesn't cost in the league of the gaming mice but given you can pick up a mouse for a couple of pounds the £20 for this is not cheap and I am sad to say this is not up to the solid build quality of previous MS mice, it feels light, the plastic feels cheap, the buttons click positively but actually vibrate the whole surface. I quite like the slightly rubberised surface but that will wear off as in past experience so I suspect in another year I will be looking for me next mouse.