1) As always make sure you have nothing running besides the game. I even tried turning off antivirus but that didn't seem to make a difference for me though it might for you.
2) For nvidia users a helpful tip is try the nvidia beta 301.24 drivers. Some have also posted success with older versions 280.xx but I have had the best luck with the beta drivers and hope that the next version will be further optimized for D3. If you're using 301.24 you will get some extra features. I have created a profile for D3 and overridden the following settings in the nvidia control panel: perf mode: single display, pwr management: max perf, triple buffering: on, vsync: adaptive. On 280.xx it is noted to set the max pre-rendered frames to 0 (this option is not available in the beta drivers).
UPDATE FOR NVIDIA USERS: New drivers release by NVIDIA! Enabling Adaptive VSYNC in nvidia cont. panel and disabling in-game may improve performance! See more info here: http://us.battle.net/d3/en/forum/topic/5270829425. Many thanks to KelJar for the tip!
For ATI users make sure you are on 12.4a drivers. I don't have a radeon myself but apparently there is a radeon pro app that helps tweak the settings and reduce stutter. Sorry I don't have more info on this but if you check the forums you should find more details.
3) Quad core users are reporting performance improvements by setting the processor affinity to 1/2 cores instead of all. Google processor affinity for more info, it's pretty straightforward. I have a dual core and this did not help for me.
4) There is a d3prefs.txt file that seems to rate your system when the game is first launched. Users are reporting improvements when setting HardwareClass to 1 (typically it will be a higher number).
5) In-game settings: the biggest changes that impact performance for me are vsync, shadows and anti-aliasing. I have also disabled the foreground FPS limiter. Note to vsync: it seems best with adaptive vsync on in the nvidia control panel. Your mileage with vsync may vary but for me and my gtx550ti it makes a big difference. Anti-aliasing OFF seems to give a slight performance boost.
6) Windowed or fullscreen windowed. Simply changing the game out of fullscreen mode seems to stabilize the game's framerate quite a bit. I use fullscreen windowed mode.
7) RAMDISK. This one takes some time but for me has made the biggest difference to help alleviate this bug. I doubled my RAM for under 50.00 and have the ENTIRE game loaded into RAM. I'm using DDR3 RAM which is still significantly faster than SSD. I did a two part guide, the links are here:
8) Don't give up! The lack if response from Blizzard doesn't sway my belief that they are aware of this issue and are just keeping quiet. My hope is they are working hard for a fix and hopefully we'll see that fix sooner than later. Don't be afraid to call in to customer support and tweet your concerns with @BlizzardCS. With enough visibility if they are not making this issue top priority, hopefully they will.
Good luck and like the rest of you I am eagerly awaiting a reply from Blizz!