so glad i found this thread - been having this problem for easily 12 months...

i ended up reverting to using linux which seemed to help things for me (c3, i had exactly same experiences as you, seem feeling, same delayed hit reg, lg being down at 30% - if i boot in to the linux partition, same config, its back up at 40)...

now they have bombed off linux, im stuck with having to find a resolution in windows.. already installed win 7 64, win 8 64, and currently testing xp sp3... delays in all of them, if i reboot back in to linux and play under Wine, its almost fixed like before, only Wine adds some other issues of its own : (

point to note, im also running a Gigabyte Z68 UD3 motherboard, with a intel 2500k, 6950 and 8gb ram - seems a few of us on gigabytes having issues

Will add to this as i start to test tomorrow, checked my DPC and its ranging from 8-500 atm