Did my S-licence yesterday and man, that was by far the easiest of them all to get all Golds. 4 or 5 of them I got on my first try. And even beyond that, when I wasn't getting them on my first try it was cause I was hitting other cars from being so aggressive and getting DSQ'd. That was before I found out it wasn't even that necessary to do so on most of them but whatever, I kept being aggressive and just found them really easy as long as you didn't get disqualified. IMO S was the easiest to gold, then A, B, and IC were similar. IB and IA were a bit harder (although IA's final mission was really easy for me).
Overall there were about 3 tests I had a lot of trouble with and took me a while to do. One was IC-1 with the Aston 1000m braking, Nurburgring Dunlop curve with the Renault (B licence?), and the slalom wit the FT-86 in IB, although the latter I only tried around 10 times the first time, the I came back the next day and got it in my first try. IC-1 was just... man, that was ridiculous. All or nothing really. You had to be so damn precise or you had no chance whatsoever. The Renault on Nurburgring, I just remember how frustrated I was with that and it took me 20-30 tries. Also the BMW 1 concept on the following corner took me a while too, maybe 20-30 as well.