We have made an attempt at using a popular manufacturer who will remain un-named in a couple of our VDI clusters. While the GPU maker and VMware have been making some progress in this space I would characterize it as in work at best. You will add significant overhead to our administration of the platform. You need to manage it at the host BIOS level, the host OS level (VIB) and significantly at the VM OS level.
We have not seen the payoff we were hoping for by any stretch in reducing CPU commit and we frankly are not using it much at all. This may change and I think vSphere 7 is a bit better in terms of compatibility. Personally I would go with better CPU's to start with. The Intel Platinum CPU's with high core/frequency have been very good for our other VDI clusters.
I'd also look at the app mix your users regularly use.. IE can be really hard on CPU for legacy apps like we have.. but I'm not that in touch with the app space since I'm in the engine room.
My 02.
Fish