Pros: Pretty good feel, great button placement for the thumb with both buttons having a tactile difference. Detent mouse wheel with no side-to-side tilt, just like I wanted. BlueTrack works really well. Even the pads slide nicely.
Cons: The buttons seem to have a delay between the click and the response in Windows while the mouse is in motion, especially the middle mouse button. This leads me to having to re-click where I meant to click.
Summary: I sit at a desk for hours, and use a mouse a lot, so having one that was comfortable is important, Microsoft seem to make mice that fit my hands better than logitech, and this one fits fine and just works... I tried a colleagues mouse before buying this, and I'd advise anyone to try the feel of a mouse before buying if it's anything more than an occasional use device.
Summary: Bought this because I suffer with carpal tunnel so wanted a large mouse with a comfortable shape and this is OK perhaps not the best on the market but for the price can't complain and it does give some relief.
Summary: Nice, simple mouse. A little light for those who prefer a heftier one but mostly good. The extra buttons are positioned so you don't press them by accident but it's easy to reach them as long as you haven't got little hands (some people may find it a bit of a stretch). Only bad point is that the new keyboard and mouse centre software is a bit bleh and over-engineered - the old intellitype interface was much better.
Summary: Very comfortable shape (provided you're right handed) and good tracking accuracy on all the surfaces I have used. Loses a star as the middle click (mouse wheel) doesn't register every so often but no deal breaker. Great value overall.