Do check for the buttons for wear and tear. Our one, the paint on the AC button is faded after a year. Local CKD one.
If equipped, do check the Adaptive M Suspension. My AB mechanic said if there are squeaks (it seems common when driven too hard, i.e.:not slowing down on bumps), must get it changed under warranty, or else it can be expensive.
Not too sure if you know, but the key does hold all the info of the car, so if you can get someone to plug in the key to a PC and print out a report, you will get a clear pic of what is going on under the hood and any necessary maintenance coming up. And also it will tell you how the driver has been using the car. Yes, when we sent in to the dealer for service, it shows average speed, distance travelled in the last two weeks, average monthly mileage, remaining part lifespan and all. Awesome.
But seriously, it is a very good car. There's BMW. Then there is the rest.