got to play it at PAX. I've got to say, I was very pleased with the implementation of VATS. The transition to and from vats is very fluid, and easy to manage. It seems like it would be very difficult to 'run n gun' the whole game, at least with a console controller. VATS will be probably be relied on for the harder, more strategic battles, and the FPS style will allow you to avoid long boring encounters with low level enemies (rad scorpions anyone?), or can be used as a fall back for when you've run out of AP and just need to finish off an enemy.
I obviously did not get to play long enough to speak on the depth of the game, but in a very short time i was able to swindle a woman out of some caps for a job I never intended to do, and also inadvertently decapitated some escaping slaves.
It seems very close to oblivion in that there will be many many quests and side stories to explore. However, the combat does seem much more fun than oblivion ever could be. There were points at which NPC's were engaged in fighting, however it wasn't clear whether or not this was scripted.
I don't believe there will be scaling in this game, or if there is, it won't be nearly as ridiculous as oblivion.
If you hated oblivion you probably won't dig Fallout 3 all that much.
However, if the idea of a tweaked (the characters are no longer completely homely) and more polished 'oblivion with guns' appeals to you, then you'll probably enjoy it.
For me, this is a title I will definitely be purchasing at launch.