USAA made purchasing my Z the easiest thing ever.
1) Fill out form on USAA. Pick car, find dealer.
2) Wait for dealer to email/car with pre-negotiated price.
3) Go to dealer
4) Get VIN and switch over insurance
5) Print check from USAA
6)
I actually used the USAA APR as a jump-off point and let the dealership get me a lower one, so I had to do more paperwork than what was realistically necessary. If I can save a 0.5%APR though I'm doin it.