Well, I can tell you that for me, I sold my netbook (an Asus EEE PC 1000HE, pretty nice as far as netbooks went) when I bought my iPad. For my needs, the iPad does everything I was doing with the netbook, which was essentially: email, Facebook, YouTube.
Could the netbook have done more things than the iPad? Of course: run arbitrary Windows apps, install other OS' like Linux or even OS X, use USB ports, card readers, webcams, play games, all that stuff. But in practice, I didn't need all that stuff, and given the trade-off between a machine that can do all those things, or a machine that can only do a subset of those things, but damn, is it ever sexy and fun... the choice was obvious.
Sounds like there are plenty of other people who were in the same boat.