It's nice having a PSP, even though there's really not a tremendous amount of stuff I can do with it; I put God of War aside so I could play the PSP GTA games, and I haven't even touched the Crisis Core Final Fantasy game yet. The problem is, all those games are somewhat... involving, and you kinda need sound in order to get the full experience, and if you put them down for more than a few days, it's harder to pick them back up and remember what's going on. One of the reasons why I like the DS so much is that, unlike the PSP, there are lots of puzzle games that don't require sound or any complicated set up - if I'm on the subway, or simply playing before bed, I like the idea of simply being in a puzzle, and not having to get involved in some sort of story - I like exercising that specific part of my brain.
Which is why Crush is such a nice change of pace, as far as the PSP goes. I'm already thoroughly entranced by the 2D/3D mechanic because of FEZ which runs along very similar lines, and Crush fills the logic puzzle / no-sound-required PSP void quite admirably. If anything, the game is proving that my brain may not quite be ready for this kind of puzzling; while the game does a pretty good job of easing you into the mechanics, it also ramps up in difficulty at a somewhat accelerated pace - well, at least for me it does.
It's certainly worth at least a rental; there are only 40 levels, so that might not necessitate a purchase. At my current rate, though, it's doubtful I'll see them all any time soon.