when sam (my son) was 3 he was running windows xp in beta with a simple web game i had created for him (webpages with shapes, colors, letters and numbers - hyperlinks below the correct answer and a sound file to ask a question ("find the 6, sam"). it took me a long time to create and get exactly right (i originally had the navigation between the games written - sam, although gifted, couldn't read words just yet - i rewrote the navigation with a picture of shapes, colors, letters and numbers) but he spent a lot of enjoyable hours with me on one of my two desktop computers playing that one web game. now that he's 10 he has his own laptop (a d620 emachine that i'll write more about later - great system, though) i've decided to turn him loose in windows 7 ultimate. he took off into the types of things he does now (web videos and searching using searchandgive.com earning money for his school every day). i'll share more about his experiences in the beta later.
soon i'm sure i'll get my dad and daughter to test windows 7 as well, but sam has always been the first to test this kind of stuff for me.