My desktop runs on an NForce 4 chipset with the integrated gigabit Ethernet. It is connected to a wireless router that has gigabit LAN ports. I also have a laptop with an Intel 82573L giagbit Ethernet controller and I routinely see transfers between the two that are HDD-limited by the laptop (30 MB/sec or so.) Fake-data speed tests put the transfer speed at 930-960 Mbps between the two machines. So, whatever is going on in your case is not affecting all NVIDIA NICs.
Quite right, I have several nvidia boards and the speed on them in Gbit mode is simply fantastic. The bottleneck is usally the drive that's getting written too. There was an issue with Vista on Nvidia nic's being limited to 100 mbit speeds, I don't know if that has been cleared up, but on linux or XP I haven't had an issue with them.
I did not write that nforce 4 desktop boards have got problems, I only had this issue with a hp laptop - that had this _hardware_ problem, as it was there with pxe boot _and_ win too.
I know you didn't- I was just commenting that not all NVIDIA Ethernet controllers had problems. You mentioned that you had an NVIDIA Ethernet controller that had problems without mentioning the chipset or notebook model. I assume you made the comment as a warning to a potential buyer of a device that contains an NVIDIA Ethernet controller. I didn't want the OP to erroneously get the idea that all NVIDIA NICs have problems or that the driver malfunctions on all NVIDIA NICs as that is not true.