Build 28 is available now as a full setup.  Even though this is a development build we included a full setup for testing with the largest number of people.  The one drawback to this is that the setup will force you to remove previous installs, so you can't have Build 25 and Build 28 on the same machine in the GAC.  If you want to keep Build 25 around make a copy of the DLL from the \Frameworks\Net 2.0\Bin directory for linking direct against for testing.  There are a number of small fixes included in this release as well, but the big change is the query optimizer from Build 27 continues to improve.  If you never tested Build 27 pay close attention to your JOIN and UNION clauses.  Many of them can now be optimized with the new tool internally and run much faster.  But there may still be some problems undiscovered.  Test, test, and retest.