I have 2 PC's and noticed that I was getting around 20FPS on my aged Xeon E5450 (identical to the Intel quad core QX9650 CPU). With my i5-3570K running @ 4.3GHz I can get this up to 40FPS (bottom right corner of Copperlane).

I've heard quite a bit about the MSAA tweak, but i've unfortunately discovered with a bit of trial and error that the GPU isn't the bottleneck. 4x AA on/off has no impact on frame rate on either my slower machine (Xeon E5450, Nvidia GTX750 1GB) or my faster machine (i5-3570K, AMD Radeon R9 280X 3GB)

Here are some CPU utilization figures with my i5-3570K @ 4.3GHz (bottom right corner in Copperlane - Defiance Bay):

PillarsOfEternity.exe - Changing the CPU affinity (no of available processors given to this program):
1 core enabled: 19-20 FPS (100% Core 0)
2 core enabled: 35 FPS (100% Core 0, 100% Core 1)
3 core enabled: 39 FPS (70-80% Core 0, 70-80% Core 1, 80-90% Core 2)
4 core enabled: 39 FPS (60-75% Core 0, 60-75% Core 1, 60-65% Core 2, 50-60% Core 3)

GPU load @ 35-40% with 4 core's enabled, so certainly not a problem for the GPU.

I've tried checking the Obsidian forum for any mention of upcoming CPU performance improvements in patch 3.0 but it isn't looking promising.

Some good news. Patch 3.0 seemed to have improved performance (from version 2.03) in copperlane, defiance bay, for me.

i5-3570K ~52-55FPS in the same location (up from 39FPS)
Xeon 5450 aka Core 2 Quad QX9650 ~25-26FPS in the same location (up from 20FPS)

So around a 25%+ improvement in performance. I'm surprised there is no note of this in the patch log; it is definitely worthy of a mention.

Still seems too slow given the amount of 3D rendering the engine does, but good to see a noticeable improvement here!

never had such huge drops but i can confirm that things seem somewhat more fluid with the 3.0 patch. 4GB but worth it.