I purchased an inventory car with the showroom discount also. It seems oddly vague, but like others have said, just go over the car with a fine-tooth comb, looking for the less than obvious damage.
Items I found at deliver: said:
Door seal was ripped
Buffing compound filled the pano-roof rails
Door sills were scratched up quite a bit
Exterior door trim was misaligned
All of those items were addressed quite rapidly.
A couple weeks later I was having issues with the UMC, so I took it in. Evidently someone had swapped their old (2013) charger cable and adapters with my (2015) kit, while being used as a loaner. They immediately gave me a new cable and bag, however it took a few weeks to get the adapters swapped out.
A few months after that, I was swapping the 21's that came with the car for my 19's I use in the winter. I noticed that one of the wheels had been painted black on the inside drum. I brought it up to the Service Center and they said it was my eyes. I said I don't think so, look again. Then they said the color was just off a bit from the factory. I said I don't think so, look again (it was clearly repainted black just on the inner drum, while the normal paint that goes on the whole wheel is gray). They said, it's hard to tell, being an inventory car. They wore me down and I left.
The following Spring when I swapped back to my 21's, I had the Service Center put new tires on, and after which I noticed that tire was leaking. I brought it back in and they said I had a cracked rim from hitting a pothole. I didn't recall hitting any potholes, and the wheels hadn't been on the car over the winter. I took the wheel to a Tesla recommended repair shop and they told me that the wheel had been repaired before, and not a quality job at that. I went back to the Service Center and they told me it had been too long since I took delivery and that they couldn't guarantee that I hadn't done that myself. Then when I pushed the issue, they pointed out that the car was an inventory car in a different state and they couldn't know for sure what had happened down there, but that if it was reconditioned it was done right, not that we are saying it was reconditioned.
Moral of the story: look at things you wouldn't expect to look at; it was an inventory loaner, people are shady.
Oh, and request they tell you any damages that were done / repaired while in inventory.