Without the Mass win the Tea Party has less credibility to helicopter in fringe/untried candidates in senate races, and Reid, Boxer and ?delaware? may not be so lucky (it's politics - with every win there's a boomerang ..)
California, I seriously doubt -- both the primary and general were pretty lopsided OTL. Nevada Republicans were going to nominate someone either way, so that race probably doesn't change much. Delaware, I'll give you -- OTL, O'Donnell beat Castle by just 6.2%, and without a Scott Brown victory, TP people may be less enthused in blocking the clearly more electable Republican. So we'll say that's another switch TTL. Then there's the potential Democratic keeps...
There might have been some knock-on effects in the Senate races. In Indiana, Dan Coats may not declare and Evan Bayh may choose not to retire, so Democrats might be up one additional Senate seat. And in WA, Dino Rossi may not run, although he didn't win anyway, so no big change.
I'd add that with Ron Wyden's seat safe(r), National Democratic monies are going to be freed up to spend in other states. I'm guessing that means the Dems keep the Massachusetts seat, Evan Bayh's seat, and one more, probably Illinois or Pennsylvania, since they were the closest Republican gains OTL (I prefer Sen. Sestak myself).
Combined with Mike Castle's win in Delaware, that puts the Democrats new majority in the Senate at 53 -- certainly not a lot better, but still...