Take it from someone that did get a maintenance warranty back in 2008....
- If you're 6MT, make sure your dealer covers the clutch. Some dealers wont, mine does. I'm on my 2nd right now. As my SA told me, any sign of slipping they will change your clutch to a new one which is nice.
- I had all 4 brakes changed
- I had all 4 rotors changed
- Peeling steering wheel trim covered, from what I was told from maintenance not CPO
- driver side door handle trim peeling, also covered.
- wiper blades changed every time I bring it in
- o2 sensor changed
- brand new spark plugs twice
- micro air filter changed everytime, although this is usually by request
- discolored side mirrors covered on both sides, from what I was told it came from maintenance not CPO for some reason
I mainly only got it for the clutch, but if you use it then yes it is definitely worth it. If you don't use it and forget about it, then no don't get it. Personally if anything is a bit off on the car I don't mind taking my car in Sat morning, getting a starbucks coffee, ride a loaner x3 (usually by request) for the weekend, and get a nice performing car on Monday morning.
Here is a list of all the items:
http://www.bmwusa.com/mpdisclaimer