The biggest improvement is that it now designed and tested to work in a multi-threaded environment.  Previous releases of SQL CE only worked in client-apps and would corrupt/crash in server environments.  SQL CE 4 specifically supports server scenarios.

We also now support shared hosting and medium trust - which wasn't supported before.  We are also updating SQL CE's SQL support to be more compatible with SQL Server and enable easy optional migration.

Hope this helps,

Scott

The announcement of "New Embedded Database Support with ASP.NET" is enough to make me yawn. What is great is that it is actually SQL CE 4 and has the major improvement of allowing multi-threaded access.

Believe me, it is a pain to ensure single-threaded access in a multi-threaded app with needed continuous access to an embedded database. Especially when you didn't realize that random corruptions happen with multi-threaded access.