SQL Server 2014 CTP2 is now available. This is the last public beta before the final RTM release. So, if you like playing with new features and experimenting before everyone else then this is the download for you.
CTP2 offers some new enhancements with In-Memory OLTP, aka Hekaton. I'm interested to see the new range indexes work with memory-optimized tables. In CTP1 we only had hash indexes.
Kalen Delaney has an updated white paper available. If you want read more about Hekaton under the covers, then be sure to check it out.