I had my fuel gauges replaced in the M3 about 4 weeks ago. According to my service advisor, there are three know issues with all e46 cars...
1. Fuel Gauge, no reason was given why, just is a common problem. (Mine was replaced)
2. Window Regulators, supposedly there is/are a plastic part(s) on the window regulators that has a tendency to alter shape in the warmer climates. (My passenger door regulator was replaced)
3. Sunroof, "Just plain buggy!" (That's a quote from my service advisor, and one of the reasons I ordered my M3 without one.)