Sony has confirmed that the number of downloadable PSP games being transferred to the Vita's digital download system will be at least 275.
Not every PSP game that was downloadable on the Playstation Network will be downloadable on the Vita, but Sony is pledging to make at least 275 available. Game controls are also altered to fit the different ergonomics of the new Sony handheld.
For customers who purchased a downloadable PSP game that is on the downloadable Vita list, they'll be able to download those games for free. They are tied to each user's account. That is Sony's way of offering backward compatibility.
However, the group of gamers who bought downloadable PSP games is a significant minority of the entire PSP community. The vast majority of gamers who bought PSP games went to the local store and purchased physical game discs, which were printed on a proprietary Sony medium known as UMD.
Sony confirmed earlier this month that customers who bought a physical UMD version of a PSP game will have to pay the full price for a downloadable Vita version. In Japan, Sony offered a program that gave discounts, some of which very substantial, to those who had any UMD titles.