MBPr : GPU or not GPU

Hi guys,

I'm planning to purchase an MBPr 15". I'm IT Consultant so I'll use Fusion & Parallels from time to time for test and demo to clients.
I'll be using win7 or 8.1 but no graphic intensive software (no game, no video or 3d edit), just the normal "office" stuff.
Do you think that the Nvidia discrete GPU is a must have for an MBPr running virtual machines ? Is it worth it (the price jump is about 550$ here) ?

Thanks a lot in advance !!!

Laurent