[Edit: chopov, I just beat your time on Centrifuge and uploaded the replay.

You're right, you can do that exit from the halfpipe pretty elegently if your timing is right. Still a bit long for my tastes though...]
Reef, I just checked out your tracks. The difference between the F-1 series and the Nerves series is kind of huge.
I uploaded replays for all the F-1 series (don't know how hard you tried on the author times...). They're kinda boring in a way, but fun to race and practice steering/braking on.
The Nerves series...whew. I thought a few of them were just obnoxious...blind corners after jumps/boosts, and a lot of parts where, if you didn't know what was coming, you were bent over and soundly reamed.
I couldn't even be bothered to finish Loops, Corkscrew, Gravity, and Insane after falling off them a few times, but finished Height (mislabelled on the site as "Gravity") because it was cool enough otherwise that I could ignore the nasty bits.

Steel is the friendliest of the bunch, IMO--you can more often see what's coming.
Nascar and Speed are kind of one-trick tracks. Nascar is cool--great exercise in timing and brake/throttle. Speed is just all about precision.
Anyway, I posted replays for Height, Steel, Nascar, and Speed too (again, I don't know how hard the author times were intended to be...).
Dunno if you want any advice--but on future tracks I'd suggest trying to cut down on the blind corners right after jumps and boosts, and try to smooth out the transitions from flat to angled, rather than having an abrupt bump there.
Thanks for the entertainment.

I beat the internet; the end guy is hard.