I need to go bakc and rewatch it with my full attention being paid over the last half. That said, from what I saw...
I'd say this is Biden by a nose in a situation where, were this a football game, you'd come away feeling good regardless of which team you rooted for.
I think substance wise, Biden did a bit better as the only time he OBVIOUSLY side stepped a question was in the opening segment, and because he wasn't being pressed nearly as much for specifics. Both peoples primary focus was basically in going "This is why the other guy sucks" rather than "This is why you should elect us", but Ryan was called to be specific more and had issues with doing it well (in part because they're pla nis specifically NOT to be specific but to lay a framework and to give specifics at a point where its implimentable) and thus looked a bit worse.
I don't think either came across well stylistically. Not surprisingly, Republican friends I have think Biden looked arrogant and condenscending and Ryan looked good. Democratic friends think Biden looked like a man schooling a child and Ryan looking like that child. The more telling ones though are my apolitical friends or relatively independent ones such....who basically thought Ryan came off smarmy the whole debate and Biden came off as a jackass.
And this is genreally why I say this is a near draw and a situation where both sides come out of it better than before. This is a base election, and after the last debate the Democratic base was depressed and the Republican base energized. I don't believe this debate is going to hurt the republican base, and may even energize it a bit more due to the distaste for the way Biden acted. HOWEVER, I think Biden going on the offense as he did...especially after the Presidential debate and Obama's performance...is going to re-energize the base to a point. That energy however is going to simply be a humming build until the next Presidential debate; enough to perhaps stem the tide a bit, but they need to see Obama go on the offensive before they can attempt to turn the tide.
So in that, both sides benefit. The Democrats benefit greater, but that's because they were farther behind at this moment in terms of the enthusiasm momentum. I think this gave red meat to both bases and that's important in this electoin.
However, in terms of those undecideds and independents, I think this will have little significant impact. As I said, I think BOTH guys came off as somewhat unlikable to those who weren't walking into that debate with an inherent bias of having a distinct and definite political ideology or party they generally side with. I think ultimately it will be a wash with them.
So with this being a bit more good for the Democrats than the Republicans, and Biden I think doing a bit better on message, I'd give this a slight win to Biden but in fight terms it's a 29-28 split decision.