Silent Hill: Origins is a prequel to the entire Silent Hill series. It's not necessary to have been played the other games to understand this one, but it would probably help to get some of the references. (I haven't played any of the other games.)
Minor spoilers might follow.
The graphics impressed me from the very start. When the initial well-rendered full-motion video ended and it switched to the game's own rendering engine, I had to look at it for a moment before I became convinced that it was really being rendered in real-time, rather than being a pre-rendered animation. Of course there are clear tell tale signs (because eg. the PSP doesn't support antialiasing), but it was still rather impressive.
One thing which most impressed me was that not only does the rendering
engine use dynamic lighting, but also fully dynamic shadows (using the
stencil buffer technique). This on a handheld console! The dynamic lighting
and shadowing is used to its full in the game to create a good ambience.
In a typical console style game, the controls were easy to learn and handle.
The limited buttons of the PSP were well utilized.
While the overall route and the order in which things have to be done is
pretty linear, at a more local level the game is quite non-linear. In other
words, you are not continuously forced to traverse a corridor with no
possibility of deviating, backtracing or exploring, like in so many other
games. Some limitations to exploration were imposed, though (mostly in the
form if impassable doors).
Sometimes the camera was stuck at angles where you could not see what the
playable character himself was seeing. This was especially jarring when
you could hear a monster approaching but you had no way of seeing it (even
though the playable character could, as there was no obstacle). This made
some fights artificially difficult.
You can save only at certain save points. Sometimes these save points are
way too far from each other, and you might have to repeat lengthy portions
of the game if you die.
The difficulty of the boss fights depends completely on which weapons (and ammunition) you have. If you have a rifle and plenty of ammo for it, the boss fights become rather trivial. If you only have your fists and no weapon of any kind, good luck, because you'll need it. You'll probably not beat the boss anytime soon.
The most jarring aspect of this is that there's a fixed amount of weapons
and ammo available in the game. If you happen to waste them on easier monsters,
then you are screwed. Especially at the beginning of the game it's not at all
clear that you should conserve your ammo for the boss fights, and if possible,
just skip fighting monsters (and if you fight them, don't do so with your
guns). You could easily find yourself in a situation where you just have no
feasible weapons because you have wasted them all, and there is no ammo
anywhere because you have already collected it all, and you have a big boss
fight ahead, and you have been using just one save for the game, so you are
more or less screwed.
The game becomes a bit repetitive at points, with not enough variation. Part of this may be because the scenery themes were not always fully utilized.