How Do Tablet PC's Stack Up?

How do some of the popular tablet pc's stack up?  Tablet PC's have been around for a while, but failed to rise to the level of mainstream popularity enjoyed by notebook computers and desktops. They have mainly been used by businesses for accounting functions.  Since the release of Apples Ipad, it seems that tablet pc's are gaining momentum.  Computer shoppers are now adding a new device to their wishlists.  Some of the more popular tablet pc's are; the new Ipad from Apple and Fujitsu's Lifebook, Lenovo, HP and Gateway.