Though this CTP release is released on 14th of January, 2011, I noticed that I forgot adding my blog. In case if you haven't noticed that it's available already and want to "play" with the 4.0 CTP please download it from here. This technology preview of the JDBC driver added support for Denali. Main features which are added in this release are Type-4 Kerberos Integrated Security and client side support for "AlwaysOn" feature in Denali (our new SQL Server product's project codename is "Denali").
Needless to say, please read the license agreement in the download link and DO NOT put this versyion on production as it is CTP yet!