I can already see the 2016 elections. If Republicans do get their majority in congress, I doubt they'll work well with Obama. Possibly trying to pass ludicrous bills knowing it won't get passed, then campaign about how a Democrat President is ruining things (even more), defying the will of the people blah blah blah.
A GOP Senate really doesn't change anything from a legislative point of view. The only problem is what it means for presidential appointments and nominations. But it's probably only temporary; Democrats are likely to regain the Senate in 2016.