The RS3s have good grip slightly more than comparables such as AD08s and RE11s; once warm it is very sticky.
Turn in feel is different compared to AD08s, the sidewall is not as stiff (does not mean it is slower). I have heard that wet grip on the RS3 is also poor but never experienced it myself as I have never driven the AD08s or RS3s in wet track conditions.
I am running another fresh set of RS3s shaved to 5/32nds and heat cycled for July 4th race in willow springs. I currently still have AD08s mounted on my track wheels and will be running them out for practice before thrashing them and mounting the RS3s for Sunday's time attack.
They are also slightly cheaper compared to RE11s and AD08s. Honestly if I didn't have to run street tires, I would be running NT-01s for R compound properties.