Seeing that your chipset ranking is merely your opinion, I would like to argue a few things in favor of the ALi MAGiK 1 chipset (revision C), based on my experience with the Iwill XP-333. First of all, I have had none of the PCI bus issues that VIA boards are notorious for, meaning that I can record audio on my Audigy without crackling and other anomalies. Second, the only case of bad AGP performance I know of can be traced to the fact that nVidias WDM drivers disable AGP on ALi chipsets, the reason unknown (probably has something to do with AGP problems on the old Aladdin V chipset, but these problems are NOT shared by the MAGiK 1 chipset). There are instructions for re-enabling AGP on ALi's website. Bad memory performance, you say? My Iwill XP-333 (ALi MAGiK 1, rev. C) beats my friend's ECS K7S5A (SiS 735 chipset) quite soundly in memory benchmarks using the same CPU and RAM (CL 2.5, Ultra timing):
ALi: 1956/1787 MB/s
SiS: 1676/1608 MB/s
Finally, I don't understand what you mean by "horrible driver support". All you need is the AGP driver, and everything else works as it should. I had no trouble finding this driver on the download page.
All of the things I've mentioned, my system's perfect stability, and my experiences with other chipsets prompt me to devise my own chipset ranking (from best to worst):
1) nVidia: although there were some compatibility issues with the original nForce chipset, the nForce 2 looks hard to beat
2) SiS: The ECS K7S5A is the best-selling AMD motherboard for a reason. More compatibility than VIA at the cost of some performance.
3) VIA: Reverse-engineered AGP/PCI does lend to some compatibility issues and reduced PCI bandwidth (VIA refuses to get a proper license from Intel), but has an excellent memory controller.
4) ALI: Great stability and compatibility with the C-version of the MAGiK 1 chipset, and the performance isn't bad either. Suffers none of the PCI bus problems associated with VIA making it great for music creation and video editing. The ALi southbridge is arguably the best of any chipset, save nVidia.
5) AMD: AMD never wanted to get involved in the chipset market, but their chipsets are decent (even though board manufacturers often ditch the AMD southbridge in favor of one that has more features).
I purposely didn't rank ATI, since I don't know enough about their chipset, and I don't have any experience with it.