Every movie i've ever purchased from a hadj in afghanistan or some little old lady in the back of a restaurant in New York has done one of two things.
1)It's either completely turned me off of the movie because it was horrible. This doesn't cost a thing because now the money never changed hands; in the case of ultraviolet, i had to go get my money back for the movie being so terrible.
2)Has been awesome enough that i either simply want to see it on the theater screen with their lovely DTS surround or I want to watch it in 3D on a huge screen.
I'm a huge supporter of try before you buy. I had frozen MONTHS before it released on dvd and still ended up taking my daughters to the movies multiple times to see it.