Having struggled with my roller on my mouse being broken for the last month, I chose the Microsoft Comfort Mouse 4500. The reason I chose this over value products is that I spend at last 15 hours a day on a computer for work and leisure. In the past I have experienced hand cramp from an unsuitably shaped mouse, so comfort was of the upmist importnace to me. So far, the mouse has not disappointed. Its smooth design and shape means that the hand can sit comfortably on top without straining. For the average hand size it is not too big and therefor you dont have to strain your fingers to click the buttons. At first I thought the it was a little unsensitive and I had to push it far for the pointer to react, however, whether its me getting used to a different style of mouse, or it has 'settled in' to its new computer, this does not appear to be a problem any longer.