Summary: Bought this for my two year old. I set up a computer for him and the standard mouse was just to big. This one is perfect for him. He was able to use it right away. I did find it difficult for me to use if I'm trying to help, but I have big hands. I just installed a wireless mouse as well and I can turn it on if I need to help him. One of the reviewers said they were having problems with MS Vista.
Summary: I got this for my 3 year old to begin using with preschool software. The small shape is great for his small hands and the one button eliminates a ton of confusion (2 button mouse was a disaster). He cannot control the cursor with it just yet, but I assume it comes with practice. If it had a slower response to big movements, maybe he could make the moves, but it is fast like an adult mouse.