Most of the developers I know think of SQL Server Express as something you use while you're developing, if that's simpler than getting a full SQL onto your developer machine. They naturally assume that when you want to go into production, or if you want to use some of the higher-end features, you'll need to buy a license of SQL rather than deploying to SQL Express. Well, you may want to, but you may not have to. For example, you can use Reporting Services with SQL Express. That surprised me. The details on what sets Express apart are at http://www.microsoft.com/sqlserver/2008/en/us/editions-compare.aspx and http://www.microsoft.com/sqlserver/2008/en/us/editions.aspx. Worth a read for sure and SQL Express is a valid choice in many data situations where you need a free product, such as distributing with your own applications or for low volume, low budget projects.