I figure if they're trying to hide something, it's not worth looking at anyway. That's why I prefer buying something where it lists all the problems (with pictures). If the seller tells you the problems instead of hiding them, you're probably going to have a good sale.
I'm probably so impatient because of my last encounter. I drove there, (entire day, there and back) and just before I bought it, he said he had just registered it, and the title was still in the mail. his wife said it'd been a week or so, maybe it's in the mailbox. He said he didn't want to go out to check!
So I left there empty handed. then a few weeks went by, and I called him and he said he sold the car.
I was annoyed, but who knows, probably for the better.