The current version of SQL Server Compact has no support for 64 bits computing. While this may seem a problem if you want to deploy you application on a 64 bits version of Windows it really isn’t most of the time. In fact if you change your assembly from the default AnyCPU to x86 compatible it will work just fine using Windows On Windows (WOW).
But even better there will soon be a native 64bits version of SQL Compact. This isn’t in the beta version that is distibrited with Visual Studio 2008 SP1 beta but Steve Lasker promises it will be in the final version when that releases.
Another nice feature that will be added is support for LINQ to Entities. And that includes the designer support we now lack with LINQ to SQL.
More info about the change can be found in this blog post by Steve Lasker.