OK Skuzz... I have the same exact deal... up until the new version (2.15) I could fly with all options on and maintain 40-50FPS in almost all conditions.... now I struggle to see frame rates in the teens, even with all sliders set to performance and all options off except for detailed terrain.
I can turn detailed terrain OFF and see my frame rate pegged at 60fps all of the time, no matter what all of my other settings are at.  This is at 1680X1050 with one notch of AA at the main AH video settings window (graphics set to app controlled) and 1024 textures with the hi-res pack.
As you can see, although I don't have an I7, my hardware isn't exactly dated either.  I should add that I never got to play with patch 0, so I don't know if this problem started with 2.15 in general, or if it's a patch 1 deal...
------------------
System Information
------------------
Time of this report: 9/28/2009, 07:13:01
   Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 3 (2600.xpsp_sp3_gdr.090206-1234)
           Language: English (Regional Setting: English)
System Manufacturer: To Be Filled By O.E.M.
       System Model: To Be Filled By O.E.M.
               BIOS: Default System BIOS
          Processor: Intel(R) Core(TM)2 Duo CPU     E7400  @ 2.80GHz (2 CPUs)
             Memory: 3264MB RAM
          Page File: 448MB used, 5698MB available
        Windows Dir: C:\WINDOWS
    DirectX Version: DirectX 9.0c (4.09.0000.0904)
DX Setup Parameters: Not found
     DxDiag Version: 5.03.2600.5512 32bit Unicode
------------
DxDiag Notes
------------
  DirectX Files Tab: No problems found.
      Display Tab 1: No problems found.
        Sound Tab 1: No problems found.
        Sound Tab 2: No problems found.
          Music Tab: No problems found.
          Input Tab: No problems found.
        Network Tab: No problems found.
--------------------
DirectX Debug Levels
--------------------
Direct3D:    0/4 (n/a)
DirectDraw:  0/4 (retail)
DirectInput: 0/5 (n/a)
DirectMusic: 0/5 (n/a)
DirectPlay:  0/9 (retail)
DirectSound: 0/5 (retail)
DirectShow:  0/6 (retail)
---------------
Display Devices
---------------
        Card name: NVIDIA GeForce 9800 GTX+
     Manufacturer: NVIDIA
        Chip type: GeForce 9800 GTX+
         DAC type: Integrated RAMDAC
       Device Key: Enum\PCI\VEN_10DE&DEV_0613&SUBSYS_0592196E&REV_A2
   Display Memory: 512.0 MB
     Current Mode: 1680 x 1050 (32 bit) (60Hz)
          Monitor: Plug and Play Monitor
  Monitor Max Res: 1600,1200
      Driver Name: nv4_disp.dll
   Driver Version: 6.14.0011.8585 (English)
      DDI Version: 9 (or higher)
Driver Attributes: Final Retail
 Driver Date/Size: 4/30/2009 22:02:00, 5896320 bytes
      WHQL Logo'd: n/a
  WHQL Date Stamp: n/a
              VDD: n/a
         Mini VDD: nv4_mini.sys
    Mini VDD Date: 4/30/2009 22:02:00, 8055584 bytes
Device Identifier: {D7B71E3E-4553-11CF-575B-992503C2CB35}
        Vendor ID: 0x10DE
        Device ID: 0x0613
        SubSys ID: 0x0592196E
      Revision ID: 0x00A2
      Revision ID: 0x00A2
      Video Accel: ModeMPEG2_C ModeMPEG2_D 
 Deinterlace Caps: {6CB69578-7617-4637-91E5-1C02DB810285}: Format(In/Out)=(YUY2,YUY2) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_PixelAdaptive 
                   {335AA36E-7884-43A4-9C91-7F87FAF3E37E}: Format(In/Out)=(YUY2,YUY2) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_BOBVerticalSt retch 
                   {6CB69578-7617-4637-91E5-1C02DB810285}: Format(In/Out)=(UYVY,YUY2) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_PixelAdaptive 
                   {335AA36E-7884-43A4-9C91-7F87FAF3E37E}: Format(In/Out)=(UYVY,YUY2) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_BOBVerticalSt retch 
                   {6CB69578-7617-4637-91E5-1C02DB810285}: Format(In/Out)=(YV12,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_PixelAdaptive 
                   {335AA36E-7884-43A4-9C91-7F87FAF3E37E}: Format(In/Out)=(YV12,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_BOBVerticalSt retch 
                   {6CB69578-7617-4637-91E5-1C02DB810285}: Format(In/Out)=(NV12,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_PixelAdaptive 
                   {335AA36E-7884-43A4-9C91-7F87FAF3E37E}: Format(In/Out)=(NV12,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_BOBVerticalSt retch 
         Registry: OK
     DDraw Status: Enabled
       D3D Status: Enabled
       AGP Status: Enabled
DDraw Test Result: Not run
 D3D7 Test Result: Not run
 D3D8 Test Result: Not run
 D3D9 Test Result: Not run