I have the same kind of performance, but only at the beginning.

In fact, the issue is not the speed, it is good. But after hours of usage transfers are becomes laggy (after 6-8 hours a 56K modem would be more efficient ^^). This is not the case with the 100MB interface. In short, max transfer rate of 1GB interface is always ok, but it is becoming unstable over the time (transfer going up and down all the time, with stalled periods).