I agree, the cars on the whole feel much better, the supercars appear to be drivable now, I gave up with them in 5. Same with the group C, I drove the 787B and it was great.
I find the 2015 Lotus F1 car to just be ridiculous. The acceleration and handling scores aren't that much higher than the Indycars; although on a track I know it is in another league. It just spins up though, you have to be super careful about accelerating out of any corner. If you hit about 60 throttle in 1st, 2nd or 3rd, it spins the wheels. It just doesn't seem to have enough grip or downforce. The telemetry says it has about 980 bhp, but less than 300 ft/lbs of torque. If you accelerate in a straight line, it's kind of ok, coming out of a corner, I have to baby it.
I don't really get it, other cars have more power/torque, perhaps it's just the amazing power delivery of the Mercedes power unit and Lotus couldn't afford to make it drivable.
In general I feel as standard the cars don't have enough grip. Sometimes you think you've gone in to a corner slow enough, the nose has turned in fine, but the back isn't happy.