EF 4.1 Update 1 (EF 4.1.1) has been released a few days ago.
The important point is also EF 4.1.1 Code First Migrations August
2011 CTP Released:
This is really important for people working with Code-First because it allows
to change your Entity Model and then upgrade your database instead of having to
re-create the database from scratch.
Even though EF Code-First Migrations is still a CTP, it is something just for your development time, it won't impact to your production code dependencies which are RTM dlls/assemblies (EF 4.1.1).
EF 4.1.1 (Update) is a release version (RTM).