never thought I'd actually be playing half life on my psp. I played through the training level and it runs pretty well, occasionally dips below 20fps but stays mostly in the 40fps range. one might have to do some optimization to get the most of it.
I tried it first with a non-steam copy I had and it would throw node graph out of date errors and my psp would crash, new game didn't work at all, but the steam version works. It takes ages to load though and the sensitivity on the joystick is set way too high and for some reason it's not possible to lower it in the game menu, you have to do it manually in the cfg file. the buttons also needs to be reconfigured, what I did was map the forward button to X and only use the joystick to look around. that frees up the d-pad, so you can then map basically all the actions you need. the psp is obviously not made to run this in any sense, but it kinda works