If you expected the Vita's "UMD Passport" program to be comprehensive, allowing you access to downloads of all your UMD-based PSP games at launch, you weren't paying attention to the last console generation.
Sony posted the list of games available at launch in Japan, including 262 games from publishers like Atlus, Nippon Ichi, Acquire, Kaga Create, Alchemist, Tecmo Koei, and SNK. As of now, no games from major publishers like Square Enix, Capcom, EA, Namco Bandai, Sega, or Konami are available for download. Sony does say elsewhere that other publishers, including all those, are "planning" to support the program.
The "discounted" prices for UMD owners to get Vita-playable downloads of their games range from ¥500 ($6.44) to ¥1,500 ($19.38), with one pachislot title as a ¥2,400 ($31) outlier.