This morning the SQL Server team announced the release of Service Pack 1 CTP4 for SQL Server 2012. Back in July I talked about CTP3 and how the release contained BI features only; no fixes. The newer CTP does have fixes and other engine enhancements as well; there is even proper documentation in Books Online about the enhancements. The download page also lists them:
The build # is 11.0.2845. There are 37 fixes listed in the knowledge base article, KB #2674317 (but it's possible that number will change before RTM). Many of these fixes are ones that were included in RTM CU#1 and CU#2. No fixes from CU#3 are currently present in the SP1 CTP.