I bought a PSP when it first came out, and it was fantastic. The graphics were spectacular for a handheld device and that screen was so huge. Then the newness wore off, and it just became stale. The problem was really the games. The games weren't being developed for a portable in mind, they were stripped down PS2 games.
And then, I was there when all the homebrew started (anyone remember swapping memory sticks to play homebrew?), and that piqued my interest for a while, but even that lost its luster.
I've been toying with the idea of picking up a cheap PSP to play MGS Peacewalker, but I don't think I am. MGS used to be my favorite game series... now I just can't get excited for it.