I have a Marvell Yukon, not sure the model off hand. I am currently using the skg.kext, seems to be the only one I found to get my ethernet working.
Although everything does work, and in the properties it shows connected fine at 1000mb/s, but I notice a considerably difference in page loads in Leopard then in XP.
Does any one else have this problem, I guess I can just deal with it.. as its not that bad. I just know it shouldnt be taking 15 seconds for a page to load, when it normally would only take about 5.