Just my two cents as well:

We bought our X5 in September '08. It's a 2005, 3.0i, sport package, CPO. Nice vehicle, fun to drive.

Highs:
1. Loads of fun to drive, very sporty. Love the Imola Red color.
2. Feels very heavy, safe.

Lows:
1. Concerned about future expenses for maintenance items not covered by CPO.
2. Squeaks and rattles.
3. Frozen door locks in winter.

Would I buy one again? Tough question. Maybe, maybe not. It's a great driving car. But I keep asking myself if I wouldn't have been better off with the Acura MDX and it's better reliability and larger cargo/passenger space...? On the other hand I see MDX's all the time where I live, not too many X5's. And I've never seen another Imola red one,