I thought the trailer looked great, myself. I feel there's a distinction between... "graphics" and art direction anyway, though.
I mean, you can have the highest resolution textures, and all of the bells and whistles imaginable but it doesn't really mean much if you don't have some quality art direction to make use of it. (This is why I never got into Crysis - sure, I have a PC that can handle it but the design just always looked uninspired and generic to me.) Bethesda's rarely pushed the boundaries of graphics power compared to other contemporary releases, but I've always been a big fan of their art direction. Few companies really put as much care into the design of their environments and world-building that Bethesda does - which is why I've been a fan of theirs for as long as I have been.
Fallout 3 may not have been the Fallout game I'd been hoping for since Fallout 2 in many ways, but one thing I couldn't hold against them was the care and detail that went into every room and vista in the game. Everywhere I looked the environment itself had a story to tell me, and that's long been a hallmark of their games; I fully expect them to follow in that tradition with this game.
The trailer got me pretty psyched. There's a lot I hope they picked up from New Vegas, but I'm looking forward to more inspired level design - arguably the world itself is the main character in these games, after all.
I didn't think the graphics looked too cartoonish, personally. A little on the clean side in the flashback sequences, but I think that was a deliberate contrast on their part. Not to mention the obvious note that not only is this a compressed video that's not going to do justice to the game's actual qualities (fine details and textures that might diminish that perceived "cartoonish" look that people are hopping on about just aren't going to show up at that level of compression,) but Bethesda's games have a tendency to look a lot better in person than they do in videos anyway. )
What I did take note of was really good environmental design and composition - as much as I liked the logic behind New Vegas' territories and settlements much of it came off rather lackluster in terms of composition, and I'm looking forward to seeing what Bethesda has been able to pull of this time.
Heck, I don't even think it's a "new" art style of anything of the sort. In reality I fully expect that what the game's actually going to look like (and what further previews will likely illustrate) is a fairly straight-forward progression of the art direction set out in Fallout 3. That was my take-away from the trailer, at least, and I was a little surprised actually at the response from some of the members here.