Actually, I'm having some trouble getting the Intel 82574 (0x10d3) to work under Lion. I've been trying the 1.3.17 version of the kext from this thread, which I've placed in /System/Library/Extensions. I verified the driver is loaded by doing a 'kextstat | grep IntelE', which shows the 1.3.17 version loaded, and it seems as though I'm looking at the correct card because en0 goes away in ifconfig when I physically remove the Ethernet card from the system. The card shows up correctly in the network preferences pane and in ifconfig, but it seems unable to pass any traffic.
(No DHCP, no response to pings after manual IP config, arp -a is empty, tcpdump -n arp on another host shows no Ethernet frames are actually being sent.). Attempts to set ethernet hardware settings manually (i.e., 1000Mbps, fdx, 1500mtu, several others) appear ineffective as well. The LEDs on the back of the card, however, consistently show a good connection.
Curiously, the driver will generate an entry detecting the cable is plugged in, with the correct 1000/fdx, but does not generate an entry when the cable is removed. ifconfig still shows it as active.
I have the exact same card working fine in a Snow Leopard install, using driver version 1.2.10. Using that version on this (fresh) Lion install gives no success either. I am using x86_64, but it appears to have the same problem in i386 mode as well.
I'm unsure of where to go from here, or how to troubleshoot further. Any advice?
Update: I built a debug version of the driver from the latest SVN sources, using XCode 4.1, a Macbook Pro with Lion, and changing the target to 10.7. No effect. The debug messages are here: http://pastebin.com/YUnBug8a