What I required in mine:
1. 10.1 inch screen. Anything less is a PDA (IMO) and anything more is a notebook (IMO).
2. 2 GB upgrade made easy.
3. Bluetooth.
4. 160 GB hard drive.
5. Minimum of two USB ports.
6. Wifi (comes on all of them).
7. Windows OS.
8. Minimum of 9 hour battery life.
In the end, I went with one of the newer ASUS machines and am loving it so far.