multi monitor support for 4 monitors?

Are there any graphics cards beside the ones from matrox that support 4 monitors and have useable OpenGL drivers available? The OpenGL drivers from matrox seems to be very buggy (following some threads in the We definitily need the features VBO, pbuffer, and S3 texture compression (S3TC)…

Any suggestions?

The Quadro FX600 PCI gives you two additional screens via PCI slot. But I don’t have any experiences in setting something like this up, but I know the monitor setup under windows can get tricky.
An SLI mainboard is supposed to do 4 screens too… (with 2 PCIe cards)