After a truly insane amount of time spent on the stuttering issue, I have finally found a proper fix. I hope someone can add this to the OP if others find it works for them.
Core i5-750 (default clocks, Turbo Boost enabled)
GTX 560 (default clocks, official 301.24 beta drivers)
7200rpm SATAII HDD (AHCI)
Vista Home Basic
I've played around in both DX9 and DX11 mode and found that frame rate limiters and/or max frames rendered ahead set to 1 and/or various Vsync and TB settings can greatly reduce microstutters, but to completely fix them and get silky smooth buttery stuff you don't need any of that! You just have to use DX11 mode (VSync enabled) and edit the registry. In the HKEY_CURRENT_USER\Software\Eidos\Deus Ex: HR folder, set D3D11_CREATE_DEVICE_PREVENT_INTERNAL_THREADING_OPTIMIZATIONS to 1. Done.
Last edited by onelifecrisis; 05-05-2012 at 07:12 PM.
Reason: Removed unnecessary crap.