Mike, you are correct about tread squirm and soft sidewalls, but for the price, I am very pleased with them. I'll post more in the road race tech forums about my weekend, but to make a long story short here, it was quite warm most of the weekend. The Sumitomo's were good for about 4-5 laps, until it got "really" hot, and then more like 3 laps until they got greasy feeling. They talked a lot, cold or hot, and had very a predictable break-loose point. I think they'll be great for the autoX, since I won't roast them near as much.
The track was pretty greasy too, with some new asphalt in spots, and drag racing the night before (turn ten leads onto the burnout box, with the strip being the main straight) My lap times were about three seconds off what I was doing last year with the Hankook Z211 R comps on a cool track, and a couple more seconds slower when it got really hot (and I got tired)
I got them plenty warm and the tread blocks distorted kind of like the Ecsta MXs used too. I'm guessing with diligent rotation I could get at least 5-6 track weekends out of these tires. That's pretty good bang for the buck. I'm surprised that GRM didn't include these in their cheapo track tire comparo last month.