I just finished reinstalling Windows 7 Pro after something bogus happening to my OS without backup. So I've just been in a similar position to you. I have an SSD for the OS, a 1TB Data drive and another 1TB Backup drive.
I moved the entire Users folder to the Data drive using this technique - http://lifehacker.com/5467758/move-the-users-directory-in-windows-7
Then I moved all of the Temp files to a folder on the Data drive called Temp, here's another guide for that - http://social.answers.microsoft.com/Forums/en-US/w7files/thread/19f13330-dde1-404c-aa27-a76c0b450818
So that gets all the App data and temporary stuff off the main drive. I then performed all the driver installs, updates and made a drive image of the OS drive using the built-in backup feature of Windows 7. Result was 12GB in size which I dumped on my Backup drive. I intend to do more drive images as I get all my software on there but I will keep this original in case the very worst happens. This article basically outlines the Windows Backup feature I believe - http://techreport.com/articles.x/17178
I realize this might not actually help you decide if you should back it up in the current condition (I personally would). If you decide to reinstall when SP1 is released you might find the above method useful though. Always nice to have an easy way to start fresh without having to reapply customisations, thousands of updates and the like. So mind numbing, I do it enough for my virus magnet relative's PCs, I've finally start cloning them too.