I've heard nothing but great things about them EXCEPT for how fast they wear down. Haven't raced on them yet.
I talked with a friend at the track (drives a really fast Mini). He had three track days on his, and they were heat cycling out. I heard a similar story from another guy who ran them the same weekend.
I've not had issue heat cycling these out for autocrosses. They need one initial heat cycles to get up to speed but they stay pretty consistent all the way to the cord. It gets harder to drive as they wear as the there are less tread block movement as the wear increases and they became more "knife edge" when they let go.
RE71R are pretty much required for current SCCA Street tire classes, either that or the Rival S. With some Kumho V720s sprinkled in if your car can run them without destroying those. On my car at least prepped for SCCA GS on the narrow wheels RE71R works a lot better than the Rival S. But they are somewhat trickier to drive as it is not a forgiving tire if you over drive it.