But you need to resister the UMD and then pay a fee to redownload a game you already own. So its cheaper just to get a PSP in the long run until the Vita has CFW and you can transfer your PSP games through the PC to the Vita.
That's another matter entirely. As is the fact that any console can have "NO GAMES" if you happen to dislike the games available to it. As it stands the Vita generally plays PSP games better than the PSP.