Gaming and video editing. The other option would be to have a setup similar to notebooks with Optimus, where I use the integrated GPU to render everything and have a single dedicated one handle the heavy lifting, or being passed through to a virtual machine when needed. The issue with that is it’s a setup not many have tried apart from the “look what I can do” factor. Say for example I want to have a video on a export on a virtual machine while playing a game on the host.
Also, on the topic of having a “hybrid” integrated/dedicated GPU setup, I don’t know if I’ll be able to use the dedicated GPU on the host right after shutting down the guest, without having to reboot the physical system. To me having 2 GPUs sounds like a more flexible solution.
If you’re wondering about the “full speed” thing, I think I already answered that question at the beginning of this post: there’s a performance loss by going x8/x8 instead of x16/x16. To be honest though I might have to suck it up and go with a mainstream platform because of costs alone…there’s a lot to think of.