I am using an Alienware m17x R4 and I have been having little mouse lags system wide. I have tried different mice but to no avail. I also have 12. 04 on an older much slower machine and don't have the lag problem on it. I don't use swap as I have 32 GB of RAM and don't need it. The system does have two gpu, Intel HD4000 and a 680M. I use bumblebee to enable optimus so that I will have better battery life.
The machine also runs all of the UI off of the Intel chip and only runs the 680m when I enter optirun before the application. I am not aware of any bugs in the Intel driver that may be causing it. Any on this problem would be greatly appreciated as it is rather annoying.