I made that exact same switch. Overall I was quite happy, though I did experience some issues the first time at the track (I encountered ABS failures which adversely affected my willingness to attack the track).
I thought balance was improved, with a little less push than the oem setup. Still obvious throttle on oversteer but fairly neutral in steady state. Cups provide a little less feedback regarding the limit so you need to be attentive in approaching the limit. However, I did not experience a slick condition due to over temp as I have with Pilots. Traction was quite steady once they were up to temp.
I noticed they took more time to get to temp. Close to 2 80-90% laps as compared to 1 lap for Pilots. Pressure rise is less as well. I pyroed mine and the temps Tire Rack indicated worked well. I can't comment about wear or heat cycle aging as I replaced the tires soon after that track event.
I mentioned ABS before as that was my exciting experience (ever lose it at 130 mph and lock the rear - it leads to a wild ride!). When ABS was off, and front to rear bias was far from ideal, I found braking to be very difficult. I was not very effective at approaching impending lock-up. Instead locking up momentarily and then reducing. Some due to limited feedback, but also due to the rear being the tire that was locking up first.
So my advice is to keep your ABS working. My problem was due to an overheated rear ABS sensor. With ABS working the tires were great for braking.
The only real complaint I have about Cups is the bump steer/trammeling effect which is much worse than the stock tires. It makes the high speed straights quite scary. No 1 handed driving with them (not that you would but I need to shift on the high speed straights at Gingerman). Bottom line is that I believe I shaved off about 2 s/lap, though I do not believe I really found the limit with the tires before my ABS failed.
