Looks really cool. I am actually thinking about learning ASP .NET, and I don't know want to buy SQLDB, so the compact for now is amazing. I want something like this because there are too many stuff in ASP .Net and I am indeed overwhelmed. This is much better as I want to really start building it one page at a time.
I am super glad I read this thread. This is so amazing for me.
Sql Express: Free
Sql Server Developer Edition (same as Enterprise but for development/test/demo only): 50 $/€