Last summer I bought my 2006 3.0si roadster with 15000 miles, already CPOed when I found it. Got the car for 28000.
Good: The CPO got me a new set of tires, and fixed those infernal cup holders. Everything else on the checklist checked OK.
Bad: When I got the car home CD player would not work. Took it back to dealer and they found 2 CDs jammed into the player! Yet it was checked off as OK. Now I'm wondering what else was merely "checked off" as OK with out really checking.
But I love my Z4 and I think I got a good buy! My CPO warranty is now good until 12/31/12.
And warranty work during the 2 year extension has a $50 co-pay.