I have played it for about 2hours now, 20ish mins of it was just remaking new characters(the start is allot better then that damned F3 vault escaping start) because I could not decide what kind of character I would be(I ultimately ended up going for a heavy science and speech guy, with some repair and gun skill) and I have to say the story is 100 times more interesting and engaging then it was in F3(I would be very disappointed if it wasn't), the exploration is very fun indeed(as it was in F3), I have yet to make it to Vegas, but I'm really looking forward to getting there, hopefully soon. The skills like Science and Speech seem to play allot bigger role in the game then they did in F3, I have already used them twice as many times as I did in a full F3 playthrough. The little I have seen of the faction system I really like so far.
As for bugs, I haven't noticed any bugs yet, just a few minor NPC walking problems like stopping for a few sec before finding their way if they walk in to other npc's, happens allot if you are escorting/following more than one npc for a quest, but this happened in both Oblivion and F3 aswell so it was expected. As for performance, it is pretty much the same as F3, with one exception, when I'm inside a house and light is shining in the window my fps seems to drop a bit and I get some minor stuttering, other than that everything is running flawlessly at High quality settings(sitting at a constant 40fps), I have a GT230 graphic cards with the latest drivers, windows 7 64bit, 8gigs of ram and a intel core2 quad cpu q9400 2,66ghz 267ghz.
That is it for now, I may write another post after I finish the game.
Also I apologize for my bad grammer/english, it always seems to go very bad when I write more than one sentence
Edit: Also a question, does the game end after the main questline like in Fallout 3 without the DLC?