Capcom developer posted some info about the PC port of RE4.
Feature wise, the new PC version is based on the Xbox 360 version, which in turn is based on Wii/GCN versions.
Many of the texture assets have been redone (not everything, mind you) from the ground up, as you can see in the screenshot gallery on the Steam Store page. I've uploaded a handful of side-by-side comparison shots for good measure just to give everyone an idea.
The game has an option to toggle between original and HD texture pack. HD texture pack is approximately 5GB while the standard pack weighs in at 1.6GB (they're in separate directories). After excluding common redistributables such as DirectX and Visual C++, the game itself comes out to about 11GB.
Similar to the Xbox 360/PS3 version, most cut scenes are rendered real time and in-engine. Some cut scenes, such as those from the Separate Ways content introduced with the PS2 version, were only captured in video. Aside from that, movies such as the opening CGI movie are naturally upscaled from the original 2005 release (again, same with all other versions).
Graphics Option - Game allows you to select whatever resolution your Windows OS supports. That said, the game is optimized for 1920x1080 (16:9) format running at 60fps and has been tested as such, but it seems to work in higher resolutions as well. Anything beyond 1080p has not been formally tested and therefore not 'officially' supported by Capcom, but I've had it run fine on 2560x1600, 2560x1440, and 1920x1200 settings. Your mileage may vary. In-menu, the game will also have anti-aliasing options up to 8X, three shadow quality settings, aforementioned texture quality toggle, full screen on/off toggle, motion blur on/off toggle, and one other 'fun' graphics option that I just won't mention at this time so as not to ruin the surprise. There are other graphics options not surfaced via the in-game menu, but I'm sure many of you tinkerers will find it without problem. Standard disclaimer: any tweaks you make outside of the game menu aren't officially supported by Capcom ;-)