I bought one of these to use insead of my wireless MX620, because in my experience wired mice are more responsive and accurate than their wireless counterparts. And the M500 is indeed more responsive and accurate (measured in terms of drawing straight lines in Paint), so it's a good mouse in that respect.
However I sent it back because I didn't like the feel of the microswitches for the left and right buttons. There didn't seem to be much travel in them and the click felt a bit "mushy" and not very satisfying. It's perhaps a subjective thing, but the microswitch components were clearly different to the MX620's.
But the main reason why you probably shouldn't buy this mouse is because you can get the
Logitech G500 Gaming Mouse instead, which is in just about every respect a superior product. Don't be put off by the fact it's called a "gaming mouse"; this just means it's just a higher specifictation and has many features that make it good for general purpose desktop use, and especially for graphics work.
Prices vary, but a few days ago both the M500 and G500 were selling at about the same price (£30-32)... I notice that today the M500 is about £5.50 cheaper, but I still think the G500 is easily worth the extra. I'm not sure how Amazon sells them so cheaply, nearly half price from their RRP and £15 cheaper than most places online, but who cares... grab a bargain while you can! The G500 has variable precision, higher reporting frequency, a nice braided cable, more buttons (to which you can assign macros), larger sliding pads, variable weighting.
The only reason you might go for the M500 is because you prefer the more sober colour scheme, or because it's apparently 6g lighter (144g vs 150g, although that's a pretty small difference).