Dead battery is the only issue I've had. On modern BMWs it's not a simple DYI swap. You actually have to reset onboard computer that controls charging of the battery and you need a dealer to do that (or something other than a simple DYI).

Before going down diesel route on a used car, consider the availability of correct fuel in your area. Some states subsidize farm industry through incentives on biodiesel, so you cannot buy any regular dino diesel. Technically, biodiesel is not approved for use in X5d and voids warranty. For example, no gas stations in Chicago sell regular diesel and I have to go to Wisconsin to fill up with regular fuel.

Also try to find one with sport package. You get thicker steering wheel, black headliner, fender flares, and wider wheels. Wheels and flares make a noticeable difference in appearance.