Other then your general, brakes, tires, suspension and some minor engine electronics nothing that major ever really goes wrong with E46's. If your under warranty with it all your problems are taken care of. Really only problems that Ive run into is when people start adding aftermarket products to their car. Just to list a few, CAI exhausts, rims, tinted windows ect. Im sure you dont really wana hear that but if you start adding aftermarket stuff to your E46 expect to have a few things your gona have to deal with. Tinted windows cause your windows to squeel and whine while going up and down. I say as long as you keep bmw parts on it your good to go.