I've got Windows 7 Professional, Microsoft Office (Word and Excel), Norton Internet Security, Catalyst Control Center, plus assorted smaller programs on an 80 GB SSD and have only 26 GB occupied, which works out to about 33% usage at this time. I have moved Windows Library files, (My Documents, My Pictures, My Music, My Videos) to my D: storage drive.
If you're going with the 64GB version of the Falcon, your OS and other essential Windows programs such as anti-virus, GPU software, etc, plus WOW shouldn't be any problem. I think you'll like the SSD. My computer at work now seems so slow it's almost intolerable. That's the problem that I see with the SSD - Once you experience it, You'll never be satisfied with anything less.