Been using an RR6 Blade for the last 2 years with no dramas, pretty bullet proof TBH. They're not that common on, but usually 1 or 2 kicking around on each track day.
The 7 is supposedly better than the 5. My 5 has 44 thousand miles on it and has been doing roughly one trackday a month for the last 4 or 5 years! It can run with most newer models, it's just me that holds it back!