All I've read about SH4 is that it ultimately hasn't done anything differently from before. It's more combat focused and the puzzles aren't as challenging, and really the only thing new is the setting (um, not in the town of Silent Hill). One thing people are complaining about is the respawning of enemies, a big minus IMO. It got relatively good scores, there are the usual glitches (controls, camera, etc.), and there isn't much of a dramatic graphical difference b/t the console and the PC version (although it's much better on Xbox compared to the weaker PS2, of course). I haven't got it yet (I have all 3 previous SH games), but I'm torn b/t getting the Xbox version and the PC version, considering the pros and cons.
There are excellent puzzles in all three previous SH games, especially the first one and SH3 (the poetry puzzles are particularly good). If you haven't already done so, play SH2 more for the poignant story and the beautiful visuals, as it's stronger in those departments (be prepared to cry in the ending). SH1, IMO, is the freakiest one out of all of them and easily the most disturbing, partly because you have no idea WTF is going on and because of the incredible 'raw' psychological atmosphere. SH3 is more simplified in terms of story and general unfolding of things, more straightforward in the horror department, but the main character is worth rooting for (she's young and vulnerable but precocious and very strong willed). Hope that helps.
