The iPad is a companion device, but a companion device that is both large enough and powerful enough to serve as a primary computer for many people. Just take a look around the web and you will see a good number of Geeks like myself who have left behind their laptops on recent travels, preferring instead to take along their iPad only.
The Tab is not that type of device, it is not able to span the category of both companion and possibly a primary computer. As I see it the Tab isn’t even a secondary computer. That does not make it a bad device, I actually rather like it under the right circumstances.
Ben nails this one on the head. The Tab is an odd device, and doesn’t really know where it belongs quite yet. That said, it’s a fairly decent device. At the very least, its shortcomings are the same as other Android devices for the most part.