I bought a Logitech MK-550 keyboard from Amazon and installed it. It comes with a USB RF connector and a USB extension cord in case you want the RF doohickey closer to your keyboard and mouse. I installed it without the extension cord right on the back of the PC. Yikes, the same thing! I Googled the problem and discovered this.
I dealt with this issue for a while and I think I can finally say that it is NOT an operating system issue. Same behavior occurs on MAC, Linux. Also it is not limited to USB, bluetooth mice have same issues. What I found is that there's a HUGE conflict between wireless devices that share same 2.4Ghz band (mice, keyboards, routers, NICs, etc). It is not as noticeable on other devices because there's no visual indication of the problem, but the issue is there (see latency).I found the Amped WiFi analytics app for my Droid2 and installed it. Wandering around the Catican, I discovered a swarm of interfering WiFi signals. Nothing the size of an old Soviet VLF jamming station, but there was plenty of garbage in the spectrum. Adding the USB extension cord and bringing the RF connector right up close to the mouse and keyboard completely solved the problem. The distance is no different than I had for the Microsoft set, but the results are much, much better. The mouse motions are now perfectly smooth.
From what I can tell (I am spit balling here) there's too much congestion. In simple terms it is the radio band is too crowded. If you just pull up a list of routers in many areas you will at least see a dozen or more. Try this to humor yourself, start downloading something on a wireless machine nearby and see if your other PC's mouse starts to act up.