Since apparently visitors can't not get on about this in other posts...
1.) Biden won, plain and simple. Not a "knockout" or a "curbstomp," but he wins on points and wins on "TV-friendliness." Down side is that the laughing/grinning/"can-you-BELIEVE-this-kid??" schtick that the base is currently loving and pop-culture will almost-certainly process as "lovable curmudgeon" will be presented as "unbecoming" by FoxNews, Talk Radio, etc which'll keep their base suitably angry and engaged. Also, he didn't make enough of a fool of Ryan to cripple him from future political ambitions, which is what I'd have called a "knockout."
2.) Bigger "winner" than Biden was the moderator, Martha Radatz: much better than Leher. Granted, the "sit down and talk, interuption allowed at moderator's discretion" format is just BETTER for the way public-discourse is expected to be now (everyone speaks in predictable talking points, so interuptions to a certain extent is almost a given) but she held them both in place and made it work.
3.) Amusingly, the "narrative" is basically the same as the previous debate: Younger, slicker, super-smart guy who's mostly about theory (having more-or-less jumped directly from higher education to career-politics) versus older, less "slick" guy who comes in fighting and wins on experience chops. Obama gets at least two more chances to come back prepared for that, Ryan doesn't. I'm not actually nuts about that dynamic still being so effective - I think "intellectual-side" pols are preferable as leadership in our increasingly-mechanized age - but if this is what it takes to keep Republicans' hands off the Supreme Court for another four years, I'll take it.
4.) Does this "mean" anything? Not really, no. All it does is "solidify" where things have been for most of the race so far - Biden did here a micro version of the entire reason he has the V.P. slot in the first place: He makes the Obama ticket "palatable" to white/blue-collar/midwestern "swing" voters (mostly but not overwhelmingly men) who're receptive to Democrats via reliable support for union labor but are "iffy" about the young, foriegn-seeming, possibly "radical" guy at the top of the ticket. He played the role of "tuff grampa" tonight, forcing Ryan into the role of "smug punk new-hire MBA hotshot from the office who thinks he's better than you," and that's mana to that bloc.