Picked up a few of the various doors for Rhinos and Land Raiders... quality is pretty high, generally pretty easily fixed. I've only mostly bought recent releases, though...
I'd love to pick up some of the Titans, but.... too damn expensive for the usage. And also, I like the Armorcast titans better, frankly. I would like to get a Stormblade tank, though...
I do have a friend who picked up an Imperial Guard Valkyrie, and the damn thing was a mess. He had a heck of a time getting it replaced, too...