New Car Test drive - what to look for?

So...

I'm looking to buy a TLX AWD.

Obviously I want to test drive the car before signing anything.
I've seen various issues with the car.

The problem with vibration.
Does it happen with all cars, or just some.
How can I tell if it's happening to a specific car, does it have to be warm, and at what speed does it happen?

The problem with shifiting.
Does this only happen in low gears.
How hard on the accellerator?
What transmission mode?

TSB's.
How do I know if they've performed TSB's on the car?
TSB 14-016, TSB 14-017, TSB 14-036, etc?
(Are there any others?)

Is there anything else I should look for on the car?
At what point should I walk away?

Nick.