This can explain it better than I can, Gazz:

Soft Quadro

When I put my box together last fall, I bought the MSI ti4200 128MB card and softquadro'd it up to the 700XGL. It fixed a few issues I was having using the standard drivers like the infamous hypershade problems (no text on the shader nodes...no thumbnails in the shader nodes) and paintFX is a bit quicker. It's been very reliable.