I think the question of where a tablet fits in the device landscape is a good one. Here's my 2 cents: I had a netbook (Asus 1000HA) for a year and loved it to death. Ultimately, though, I outgrew it. I could deal with the keyboard, but the 1024 x 600 screen drove me crazy (I had to kill all the window-dressing in Firefox) and more importantly, with an Atom CPU it really COULDN'T multiprocess. If I ran Firefox, Word, and Powerpoint (I teach!) at the same time, it just ran too slow.
For me, I know I'd end up wanting to use a tablet in the same way I used my netbook: 2-3 programs at a time, consuming AND producing content. That's the rub...while there's no argument that a tablet is perfect for consuming, I can't imagine that it would do any better a job at creating stuff (e.g., image processing, word processing, etc.) than a netbook.
If you ONLY wanted it for movies, music, games, email....then I could see it making more sense.
-Matt