I bought it -- it's fun and worth the price. It's not going to replace Sine Mora for me as my Vita shmup of choice, but it's a good thing to have on my system.
Some of the trophies are glitchy.
Some of the trophies are hardcore.
I think, in all honesty, the only PJ game I really liked was Sidescroller.
PJM isn't my type of game and I loathe the art style.
PJS and PJS2 were just boring to me... something didn't click.
PJE I kind of liked, but some of the controls and such got to be a chore so I stopped playing.
Given my love of shmups, PJSidescroller is the closest thing I've seen to the oldschool 2D shmups like Lifeforce and Gradius. I haven't spent nearly enough time with it, but I thought it was a way better use of the assets from PJS.
With my luck, they'll port everything except Sidescroller.