I think this could prove quite interesting.
For instance, compared to the VIA chipsets, the second lot of nForce 1 and all of the nForce 2 chipsets gave the AMD platform a significant boost in performance. Not to mention that nVidia's nForce 2 memory controller was a bit more efficient and faster than VIA's too-late-released dual channel memory chipset for the socket A platform (I think it was called the KT880)
No real great chipset manufacturer has had a chance till now to get their hands into the intel chipshop market (SiS aren't known for being the fastest kid on the block, but I think VIA's stability sucks). Perhaps it could surprise us all. One things for sure, it can only be good for us, the consumer - driving prices down, and lifting performance up.