Don't forget, Street Fighter X Tekken is actually also headed to the PS Vita with an exclusive character Cole McGrath from inFAMOUS. Game looks good for a portable version and Cole seems to be a sick character to play, but the speed of the game seem slower compared to its console brother.
The game is still in the works so it's too early to judge. Their working with new tech and it's a portable device, it's forgivable for now. Hopefully we'll see a better build of the game in the next few months. Not only is Capcom working on a Street Fighter X Tekken port, they're also developing Ultimate Marvel vs Capcom 3 for the Vita too, which their trying to release together with the Vita release this december in Japan. So yea, Capcom got their hands full.