ive got a e46 328i. not an m3 I know but its a lovely car and fast and smooth on the motorway. the m3 is the daddy though and in a league of its own. still the vanos/subframe issues apply. my favourite bmthough would be the m5 of similar era. other than the issues that have been well covered the e46 is a good car. also keep the inside lip on the rear arches clean as they hold crud and can cause corrosion if not kept clean regular.