Well, I am in no way an expert, but it seems like the vast majority of transmission failures are reported in the 2000-2003 models. This, of course does not mean that those years have enough overall failures to make them bad choices (though the mileage on, and the availability of detailed records for any BMW should be seriously considered before buying). Then again, I wouldn't buy a 2000-2003 as 1. the transmission issues that have been reported in those years bother me (and I knock on wood regarding my 2005), and 2. I can't see the engine in those years being so much more durable that it would be worth the risk and the sacrifices (6 speed, panoramic, etc).