PSC2s are not even R compound tires - they are absolutely DoT legal. Plenty of guys on the various Porsche forums DD these tires. They're fine in most wet conditions, but standing water should be avoided because of lower hydroplaning resistance - even compared to typical extreme/max performance summer tires.

What you definitely don't want to do with the PSC2s is drive in the cold (just as with any extreme/max perfs). That's what all-seasons refer to - ability to drive in the cold, not really rain. Remember that many extreme/max performance summer tires actually perform better in wet conditions than all-seasons. The big question, again, is hydroplaning resistance in conditions where there is lots of standing water.

As mentioned in my thread on tires, I also got the PSC2's installed. My initial impression is that they're more planted and turn-in is improved, but haven't really driven them enough for an full impression (and certainly haven't been on the track...).