I have had pretty decent luck with mine for 5 years now, but I would be leary to pick up anything that old in terms of years. After 10+ years of being in service, there will be a lot of little thing that will fail. Commonly failed items at that age are window regulators, door actuators, cooling system, rear air suspension (self leveling only in rear on the non sport 4.4i), CV boots, and a few other common things. The good thing is that the transmission was replaced which is by far my biggest fear in mine. I am keeping mine right now because I already own it, however, if I needed to replace it, I would buy one no older that 4 or 5 years old (or go with a different vehicle altogether). Just my $.02.

__________________
2001 X5 4.4i
2002 Honda S2000