TDE is a nice feature for HIPAA compliant applications. Here is a link to a white paper on the topic: http://www.jeffersonwells.com/MSSQL2008HIPAA?
Unfortunately it is only available in enterprise and developer editions. This feature would be very nice for companies who aren't "enterprises" and don't have 25k+ dollars sitting around to spend on a processor license, but still want to be able to encrypt their healthcare database. There are many small companies that I work with as a consultant that would benefit from this feature but cannot use it because it is cost prohibitive to purchase enterprise versions of SQL Server.