Man, blogging is addictive. I'm supposed to be paying attention in this session... <g> Anyway, wanted to note a few things about SQL Express because I haven't seen a lot about this online yet - though I expect that to change.
First - some of the capabilities:
So - what we have here is a version of SQL Server that runs on your local machine - growing up to 4 gig. The XCopy deployment is also awesome. Instead of attaching/detaching the MDF, you'll be able to XCOPY the database to a new machine that has SSE running, and then just attach via the file path. Very easy deployment. Hooking that in with the new Click Once stuff in VS2005 is awesome. Deploy your winforms app securely and simply - including its database.