I recently got a Kingston V+100 96GB SSD while Newegg was having a sale ($89.99 after rebate) and I've noticed that object loading/pop up is much smoother compared to my HDDs. Level loading times aren't really that different.
RAM drive is still marginally better, but now I can use that 9GiB of memory for something besides holding Crysis.
I have noticed that the times when I get the largest FPS drop is when I am getting hit by RAC/UAC fire. It seems that all of the particles bottleneck my i5 2500K (which is now at 4.3 Ghz, but i'm not sure why I even keep going as it isn't helping at all). The GPU usage goes way down when all of these "shrapnel" particles are present. What particle settings are others with sandy bridge CPUs and/or gtx 560 Ti's using?
Honestly, I have not noticed one whit of difference in performance in MWLL between my 2600k @ 4.6GHz and my 970 at 4.2GHz. I've been almost completely GPU bound with either my unlocked 6950 or my GTX 480 on both setups.
Anyway, I run a particles quality of 2 (good performance, or medium). With it set to 3 or 4, things like smoke, explosions, and rapid fire projectiles cause my frame rates to dip unacceptably. In heavy firefights I was getting about 20fps with it set to 3 (high quality), dropping it down to 2 almost doubled my fps in these situations.