Since this thread is centered on a negative aspect to the game I'll try to comment in that spirit. I didn't mind the long driving missions but the import exporting is a let down. My plan to stock every garage in the game would be much easier if I could import (or steal) cars, mod them and then export them to myself. Seems so obvious.
As long as I'm here I've been having a lot of fun in two player, here are a couple challenges for anyone who's interested:
One player jumps in a car the other on the car. First player drives along side another car so the other can jump over to it. Then shoot the car, the NPC should freak out and drive off eraticly. Your mission; to jump back onto the original car.
See how far you can fly a plane (the Shamal is good) with the other player standing on the roof. Extra points for catching him/her if they fall off.
Huh, that's weird... What version are you playing? I'm using the USA version and I'm absolutely positive it gave me a chance to re-attach it on my first attempt, since I remember hitting a bump that made the shit fly off. Perhaps you get mission failed if the cops get the cab unattached, as opposed to you hitting a bump or whatever?