I do not have any issues with my Nvidia+Intel setup, aside from some mishaps when I upgrade my Linux kernel (Bumblebee sometimes becomes a zombie kernel module, which won't unload, and that isn't fun).
There is Nouveau if you hate closed-source or something, but it has a lot of issues right now that should be resolved in the future: namely, that it doesn't support setting the clock rate of the GPU, so the GPU always runs at boot clock speeds by default. This means that your out-of-the-box performance with Nouveau could easily end up a tenth of that of the Nvidia blob.
There's ATI, but I've heard bad things about the stability of its driver. There seems to be a lot of activity on its driver development though, so that's good.
Do not go Intel. They have yet to release a 3.1 driver for Linux/Sandybridge (while Windows has had one available for quite some time). I do not know why they are claiming haswell will do 4.0 when their driver isn't even up to par with 3 year old specifications. I'm developing a game engine and am currently waiting on Intel to release a 3.1 driver. It's sad to see such a major player in GPUs to be so far behind on OpenGL. I doubt anyone would buy Intel if their GPUs only went up to, say, DirectX 8.0...