Can't say if the dual screens is a good or bad yet. Sometimes it's distracting to shift up and down past the gap when most of the action is at the bottom half, and then something flies off to the other screen. Certainly ups the difficulty.
I'm stuck on stage 3 boss already. I keep running out of time when the two aliens merge and I can't shoot out all the blocks fast enough. Those red squares are juuuust out of reach.
In terms of PSP:
Space Invaders Extreme could have been a perfect opportunity to showcase what the PSP can do better. But nope, they had to ruin it by inexplicably leaving out wi-fi multiplayer. Do I blame Sony or Square Enix? Dumbasses.
If it weren't for the shortcomings, I would have bought the PSP version too. And SONY would have seen actual game sales on their side of things. Imagine playing full tilt with none of this friend code BS. Sigh.