On the other hand... if you haven't installed "any" extra apps then flashing and trying out OS2008 would not take long time? If you do not like it you can flash back to OS2007 as well.

You likely want to make backup of your OS2007 install. In case you want to go back to OS2007 then restoring your setup should be very easy. (And my advise to restore OS2007 backup for OS2008: Don't do it.)

One more thing... make sure you have downloaded (or know where to find) OS2007 image in case you want to go back...