The user experience with a netbook is the same as with a notebook PC except... worse. The keyboards are small and generally terrible, the track-pads are generally small and terrible and the screens are generally small and terrible. If you don't have a table to set it on, you have to hunch way over in order to use it because it requires 2 hands to operate.
The iPad takes care of all of those issues, plus it has a really great UI. No, it's not a full-blown PC. It's not supposed to be, but I think that there is definitely a market for a device like this.
Go ahead and call me an Apple fanboy if you want. I am a Mac user. I already have a MacBook, though, so I don't have a need for an iPad. But if I had a desktop PC, the iPad would be a nice mobile device for me.