I bought this to replace an Apple Pro mouse and was concerned before purchase that it would be too small. It is slightly shorter, but in day-to-day use, this is no problem at all. It tracks much faster than the mouse it replaced and, if you're right handed, can also be used with a Macbook (unlike the wired Mighty Mouse) as the cord is much longer at well over a metre. Easy to control thanks to the rubber-covered lower half.
All in all, a great buy.