dodecahedron, there are two Intel drivers for i845 chipsets, one if Intel INF which is for all Intel chipsets, and one is IAA, which is only for i845 and i850 I think.
The later does improve performance a bit, just a bit, but brings some problems. DMA is not under user controll anymore, it is controlled by IAA and you cannot change it manually. This sucks. But other than that and a few minor problems, IAA is OK.
Not necesary but sometimes better than MS drivers.