Any major problems when using a NVidia and an ATI graphic cards in the same PC?

Question

I have decided to develop a 3D game, and I need a new PC with recent hardware to use as my "baseline" for performance and compatibility profiling/testing.

Now, I would like to test it on both a recent NVidia and ATI (now AMD) graphic cards, but I would hate to have to buy two different PCs just for that. Intel/AMD compatibility is a non-issue nowadays, but you can't assume program-once-run-everywhere when it comes to 3D. I gathered that PhysX in NVidia will be disabled, but since it's NVidia-specific, and I can only have enough time to use cross-platform APIs (like OpenGL), I'm not really affected by that.

So, to restate my question: Is their any major issues (apart from PhysX) when using a NVidia and an ATI graphic cards in the same (most likely Windows 7 x64 + Linux dual-boot) PC? Will the drivers "break" each other, or cause some major performance penalty?

I would prefer answers from someone who actually done this, instead of just pure speculation base on some article, although a reference to a recent article would also be useful.

Answer 1

On the Windows side, WDDM 1.0 on Windows Vista could not use two different drivers at the same time, without disabling Windows Aero, so you had to use graphics cards which used the same driver.

WDDM 1.1 on Windows 7 is able to use different drivers at the same time, although I have not personally tested this, as since then both graphics cards in my CAD workstation use the same drivers (ATi FirePro), and my other machines have single graphics cards/chips.