As many people have pointed out, for many users the game is CPU bound most of the time. This is why for many of you, adjusting the options don't seem to help much; the options mostly affect GPU performance. In order to solve this, we need get more of the game to run in parallel on more cores. Unfortunately, this is a time consuming and fairly difficult task; code on one core has to be careful not to modify data in use on other cores. Mistakes could result in an access violation and a crash; to make things worse, reproducing the crash is difficult because it depends on timing between the cores. Writing multithreaded code isn't easy
But we are making progress - the next patch coming out has several more optimizations of this nature, as well as a fix for the target frames, which was causing some stuttering when moving around the world. This patch should go live early next week.
The main time when the frame rate is GPU bound is during large special effects right in front of the camera. We're currently adding some options to limit the number of those particles - these will take a little longer but should make it in before launch.
I can't promise these two fixes are going to make the game run like butter on every pc out there, but I can promise incremental ongoing improvement up to and beyond launch.