Try these tweaks, it's helped some alleviated their FPS issues well as other issues.
Update: 11/22/11 I've had to change quite a few of the fixes for various issues that people were having, because of Steam updating the executable for Steam. They basically encrypted the file so that pirates have a harder time of running a hacked copy on the service. Anyhow, I've been running/testing the following to ensure that it actually works and still fixes the issues people were having. So here it is.
Important note: AMD USERS: Absolutely try out the 11.11a AMD performance driver. It did wonders for my gf's computer.
http://support.amd.com/us/kbarticl [...] mance.aspx
Nvidia USERS: Use beta driver 285.79
I am running Skyrim at 1920x1080, antialiasing 4x, anisotropic filtering 12x, shadows high, Decal quality Ultra, distant objects detail Ultra, everything else on high except radial blur quality medium and I easily get 24-35 fps even in crowded areas like towns. The mods IMHO make the game look better but everyone will feel differently on what looks good to them.
(no more blocky faces, detailed faces v2, ENB series 092 version 5 patch (merged with FXAA Post Process Injector) , enhanced blood textures, detailed bodies, vurt's skyrim flora overhaul, detailed lips and high quality eyes. All of these are available at Skyrim Nexus)
My Setup
OS: Windows 7 64bit
CPU: AMD Athlon II X240 Regor 2.8ghz oc'ed to 2.94ghz
GPU: Nvidia Geforce GTS 450 1gig OC'ed Driver: 285.79 beta
RAM: 4GB DDR3
HDD: 320GB 7200RPM SATA3
MOBO: FOXCONN AM3
PSU: 450W
Update: 11/21/11 I've put in about 15 hours on vanilla settings, and 40 hours with the above mods, and 25 hours overclocked ,FXAA Post Process Injector installed (The latest ENB performance patch and FXAA Post Process Injector can be combined together and it works well, and looks great. Please follow the instructions included with FXAA Post Process file.). The 4GB Skyrim replaces the Large Address Aware and is compatible with the changes made to steam executable.
The following is what I would recommend to utilize besides the mods I mentioned above.
4GB Skyrim
http://www.skyrimnex...ile.php?id=1013 (Skyrim4GB is a tool to load SKyrin with the Large Address Aware executable flag set so the entire 4GB Virtual Memory Address Space can be used
by the game.)
ENB series 092 version 5 performance patch and bug fixes
http://www.skyrimnex...file.php?id=953 (This version works even after the steam update) I do not think version 091 works after steam update. This also fixes the shadow issue so many are experiencing.
oh and lastly, make sure you have your sound settings on 44.1 khz, 24 bit.
For unusual mouse lag/behavior:
Here's the fix:
Launch a Windows Explorer window (win key + e)
Navigate to \Program Files\Steam\steamapps\common\skyrim\Skyrim
Open SkyrimPrefs.ini in Notepad.
Locate [Controls] and then find 'bMouseAcceleration=1'
Change bMouseAcceleration=1 to bMouseAcceleration=0 instead; this will disable "mouse smoothing" and "mouse acceleration" in Skyrim.
Fix for unresponsive menu: (on-screen interface key fix)
http://www.skyrimnex...file.php?id=368
Here's my google + photo album showing the mods in use.
https://plus.google.com/photos/1125 [...] 1181143137