Different operating systems measure the latency differently. I can ping one of my Juniper routers from another Juniper router and it register the time as 0ms, where as from a workstation it is 1ms. I would not worry about it. As long as a persistent ping, ping xxx.xxx.xxx.xxx -t from Windows or xxx.xxx.xxx.xxx from a *nix box, is stable you should be fine. If the latency grows to 3ms, 4ms, and up you have an entirely different issue on your hands.
