I have been spending quite a lot of time in Paradise City the last couple of weeks and two days ago I finally completed all the challenges. I've had lots of fun doing this.
The last challenge I had left to do was the 8 player 75% Power Parking Challenge. We had one player that was online for the first time in the room and of course he had no mic. After trying to do the challenge for 10 minutes I decided to hunt him down and try to help him out. I could see that he was trying but he kept setting of the alarms of the cars... I did a couple of power parkings when he was watching and then parked in front of a car that was still untouched and after 3-4 tries he finally got it! I think this was a cool way to complete the challenges.
I have not been racing much lately. When I host races I mostly host the races from the Cagney update. I'm not very impressed with the chosen routes but the experience will hopefully be better with tweaked traffic and starting directions. I think the biggest problem with racing in Paradise City is that they for some reason put nearly all the checkpoints on intersections. If you think about it this doesn't make sense at all! It makes it virutally impossible to make a high speed race with a good flow that is easy to navigate. Checkpoints should be put in between intersections where possible. I know this will never happen because it would make racing faster and better and more like previous Burnout games and we cant have that can we? Better to use the time to even out bumps in the airfield!
I agree with ZombieTron that Burnout Paradise is more of a driving game than a racing game. And I fully understand why the telemetry for the game is showing that challenges are very popular. These numbers would have been very different if there was actually anything else to do. Personally I don't think I would have spent any more time doing challenges if racing was perfect. I have realized that this will never happen and that there is nothing that can be done about it. This makes me sad because it is so close. The only thing left to do is to surrender and join the challengeaholics in their online driving mayhem.