Sega is unwilling to give a revised Jet Set Radio release date and asks fans to keep an eye out for further announcements.
Sega's Jet Set Radio, the skater gang game that has you tagging Tokyo-to for reputation and glory, was supposed to be out for the Vita by now. The key word in that sentence being "supposed", 'cos it's not. You'll have to wait a little longer, and no, nobody knows how much longer.
"Necessary development optimizations" was the official reason given by a Sega Europe representative for the delay. Sega expects to give a revised date "soon", and asks that fans keep watching the Sega page for further details; though I notice that, at time of writing, Sega's page thinks that the Vita release is out now.
PS3 and Xbox 360 versions launched last month, so if you have those systems, lucky you. Vita owners, stay calm. Breathe normally. Try not to panic. It'll come ... eventually.