Only a few months ago, this game was definitely not headed our way, and despite a lot of subsequent shows of support, Square never officially changed their minds. However, here it is, live now on the EU PSN! Its £11.49 compared to the iOS version's £7.99 (plus in-app purchases).
That version arrived in February and has since garnered a massive 12 reviews, suggesting the mobile gaming community isn't exactly lapping it up. That may be why it has sprung up on Vita, to try and claw back some cash.
So, go get it to prove that it is worth Square's time making the port and that the Vita community sticks to its word. Remember to rate it on PSN, so we can see how many buyers there are. Quite why Square couldn't mention this as a bit of bonus news at E3, or just let us know it was coming - who knows? But get the word out there and start adventuring!