We're running VMware and I've spent a bunch of time building a template based off of our MSDN Developers copy of Windows Server 2008 R2 Enterprise. The template was built for our development environment. We're ready for production now and need to know if we can stand up VMs using the MSDN template and then change the Windows Product Key to our official MS licenses.
Yes, for Windows this is fine. For some products (e. g. SQL Server) the Developer edition is functionally equivalent to Enterprise but is a different SKU with a different license. For the OS itself it's the same bits, same edition. Just make sure you started with Volume or Retail depending on what type of license you'll be putting in.
If you made the mistake of doing the wrong license type (Volume vs. Retail) it's easy to change, in particular Retail to VL is very easy: http://justinho.com/post/2009/09/18/Converting-Retail-Editions-to-Volume-Activation.aspx
Note that some of this only became officially possible as of Server 2008 but you said you're on 2008 R2 so that's not an issue here.