I'm just going to say it, I don't see a use for SQL 2008 R2 SysPrep.
I'm generally so happy with SQL 2008R2, people often pretend they aren't with me when I get started. Really, if I want to look vaguely normal, I have to be seen with people with an even more fanatical dedication to their product like Mac users, or our SharePoint administrator. That's why it's slightly painful (although vaguely reassuring as regards my sanity), that I'm super disappointed with the much touted SysPrepability of SQL 2008 R2.
Really, as far as I can tell, it's slightly worse than nothing at all. You can only prep the database engine, reporting services, and the browser (not even the client tools and SSIS!). You can tell the prep install all you want that you want the base instance install to go to a location other than c:\program files, but it apparently knows better. It not only defaults back to c:\program files, but greys out the ability to change it once you run the complete install. It knows better than you what you want, even if you explicitly told it what you want. As far as I can tell, you can't even set the browser service to automatic, or set a default data and log location in the SysPrep.
The Microsoft article on SQL SysPrep is here
The only useful thing I can see is that it requires you to copy the install files locally so that they're already included in a template (but, surprisingly, I'm actually capable of copying files to a template anyway). I also find it weird that the SysPrep comes up as evaluation edition until it's fully installed (this is noted in the SysPrep article).
Just a big bummer, back to old school template unattended installs for me. If anyone has cool ways to make SysPrep fancy or, you know, useful, I'd love to hear about them.