2007 3.0si was a NIGHTMARE, 2008 4.8i was somewhat better, but still very bad.

Constant battery issues
Horrible transmission
Electrical nightmares (being locked in the car, daily warning messages, iDrive freezing, presets erasing, time & date erasing)
Inadequate and erratic HVAC
Headlights working one day, not the next

The list just goes on and on. Besides from a 2006 Supercharged Range Rover, the 2007 3.0si was the worst car. I hated it. Problems began within a few days of ownership too. Seriously, I spent more time in a 325i and X3 loaner, than I did in the X5. Also, with the 4.8i...I spend about as many days in an X3 loaner, as I did in the '08 4.8i. While the X3 is a little small for my taste...it is VERY reliable, easy & fun to drive and a great little suv!