It is possible to use the Win7 drivers on Win8, but the issue that I've had was that with any of the "Metro" apps, the Driver would crash forcing me to reboot.
Not a big issue since I don't really use those apps anyway, but all the default programs for files is set to use them. It was really annoying, try to open a file, and I might as well be telling the graphics driver to crash.
But I did learn something from it, Before getting a PC, look into driver support.