No, the paint doesn't have to be pristine. Mine wasn't (I just touched up whatever rock chips I could see) and the car still looks very good with the film. I get a lot of compliments on the car and film, and compared to the old school 3M PPF it's like night and day in terms of clarity and smoothness.
I'm bumping this thread due to some questions being raised in another XPEL Ultimate PPF thread, as this forum only shows threads containing posts from the last month by default. Perhaps the mods will consider making this a sticky.