There are good units in any brand as well as lemons, of course a good pdi will solve a lot of small issues on the spot, then take it for a couple runs testing all systems, make a list of problems and get them addressed under warranty.
A few exceptions to waiting to fix are water leaks, electrical problems, brake and tire issues due to life safety issues. Minor cosmetic, and nusance issues can wait and be addressed at one time vs many trips to the dealer for warranty work.
You will find a lot of smaller issues are easier to address yourself, than abandon a trailer at the dealers mercy for weeks on end.
2006 Expedition 4x4 w/HD tow package
5.4L 4 speed auto w/OD 3.73
tow rated 8200
2008 Cougar XLite 30FKS