Run all the slides in and out with you on the outside checking the seals and how they go out/in.
The bed slide - make sure it goes in and out at a constant speed and check for proper sealing. They fixed the design flaw on the 2012s but I would make sure there are no issues with the bed slide going out and in.
Check the countertops for scratches and make them buff them out if there are scratches.
Make sure you have all of the remotes - took 6 months to get the remote for our fire place.
Make sure the free standing table is properly secured.
Check the operation of all of the jacks.
Give everything a close examination - and if possible perform the PMI prior to signing the papers - they will be more apt to fix the issues prior to taking delivery of the unit.
Found this:
http://www.angelfire.com/trek/buenav...PDI_V113_2.pdf