Ok I've used these tyres. (Yes the RS version)
They are not a true semi-comp in the same catagory as tyres like the RE55, DG02Z, A048, R888 etc.
They are more in the came class as the Falken RT615's.
If you look at the UTQG rating the true R comps are all around the 40-60 mark where as these tyres I think are rated at 180 (615's are 200).
Having said that they were a damn nice tyre to use and I won the Autocross/Motokhana event at DECA in a 100% stock EVO 8MR with those tyres beating modified GT-R's using RE55's etc.
They will last 3-4 times longer than a real R comp but at the track they will be 3-5s per lap slower depending on the track.
These tyres are classed as a street tyre in the SAU VIC club championship - not an R comp tyre.
The 595SS versions are comparable to something like the Hankook 104's.