Bought it in 2004, lasted to 300k in 2012. Coolant started leaking into engine. I kept the car fully dealer serviced on schedule from 96k to 290k. Car sits low to the ground, can be uncomfortable for some and headlights of other cars shine into your eyes. Was getting about 10L/100km with 30/70 highway/city. Power windows and sunroof start to operate very slowly as the car ages. Had to replace radiator but other than that, solid.

Bought a certified used. Terrible on gas, get about 14L/100km even though trying my best to keep it down, thats with about 50% highway 50% city. Requires premium gas. Was spending about $400/month in gas alone. Super uncomfortable as the ride is way too stiff. You feel every bump and fly all over the place like you are going over speed bumps. Lots of electrical and sensor issues in BMW's. Based on a mechanics word, the X3 is one of the more reliable of the series...yet I was in every other month for a year constantly dealing with issues including transmission/gearing issues when trying to accelerate from a stop, or when turning a corner, the car would either stop giving gas or blast forward - very unsafe! Also it has a "fuel cap" sensor issue, where the check engine light comes on and you have to go to the dealer to reset it, even though you are tightening your gas cap properly. Happened to me 4 times in 1 year. Sold it after 14 months and wouldn't buy again.