Gender diversity. The new Senate will include a record 19 women--despite the fact that two current female senators (Hutchison and Snowe) did not seek reelection and their seats were won by men.
Gay rights. One of these new female senators is Tammy Baldwin of Wisconsin, who is also the first openly gay senator. More dramatically: Maine, Maryland and Washington all approved same-sex marriage by popular vote, a first (and second and third). And Minnesota declined to ban it.
A saner approach to controlled substances. Colorado and Washington State voted to legalize recreational marijuana, and Massachusetts approve medical marijuana. But Oregon rejected recreational use, while Arkansas and Montana voted against medical use. There's also the minor matter of federal law.
Representative democracy. U.S. House races continue to be determined largely by how the districts are drawn and redrawn--by partisan state legislatures. Where I live, this means Republicans didn't have much of a voice yesterday; elsewhere it's the opposite. In either case it's an outrage.