Just to add - with TDE enabled you cannot exercise Instant File Initialization for Sql Server which has been proven to speed up the creation of databases (files in windows) (for better performance).  Also, TDE adds anywhere between 1 - 30% overhead to your Sql Server mainly due to the decryption process which takes additional IO and CPU to function.  We use it on many of our Sql Server instances, and we do not notice a performance hit due to how beefed up our servers are.  While the database is encrypting, you may also notice a performance hit, but that only occurs once.