I finally got back to my beloved PS3 today and was able to get the update. As the rush is over by now, it downloaded without fault in a few minutes, no problem whatsoever.
I redid my options first, making sure everything is set alright. Then, I got myself a few 0-62 mph figures of cars that are in the game to find out if, as many people say, the new tire physics is made too grippy. So far, I have only performed a few tests with the Ford GT, but to be honest, I don't see what you guys are on about.
I remembered what somebody posted here about which tire would be which in real life. The worst normal tire obviously is some cheapo standard rubber from the rummage table, while the best N tires would be a high quality tires from a well known brand. The worst S tire would be the first sports models, something you would equip your car with, knowing that you trade wet performance for some dry grip. The best S model would be semi-slicks for that matter, just below the full racing slicks. Those are found in the R range, obviously.
So what do cars like the Ford GT come with? In real life, it comes on "Goodyear Eagle F1 Supercar" tires, which are somewhere between the worst S and the best N tire in the game. So, I got into the car and gave the worst S compount a hand-timed 0-62 run on the Daytona straight. I was presented with a 0-62 time of 3.7 seconds, which is somewhere between the optimistic US-figure of 3.3 (also 0-60 mph) and the pessimistic European figure of 3.9 seconds (both according to Wikipedia).
Sounds alright then, so let's give them a go on Suzuka. And what shall I say? I was easily able to break traction in 1st gear in every situation. And in 2nd and 3rd, stomping on the accelerator while being on the edge resulted in the back of my GT stepping out. Overall, the grip felt like I would expect it in the real car.
Therefore I must raise the question: how is this less realistic than before? I'd say it's pretty much on the spot now.