As soon as Windows 7 RTM got released I upgraded my main computer and my laptop. On my main machine I put Windows 7 x64 as I have 8 GB there. Everything worked great except the network card. I was unable to get more than a couple of hundreds of KB/s of transfer speed.
I updated the drivers to the latest version from Intel, but it made no difference. Of course this was a show-stopping problem because backups takes forever and even browsing photos from a network share is simply impossible.
I’ve finally solved the problem purchasing a 6 € Gigabit network card. It works just fine and now I’m getting around 12 MB/s again (my network is 100MB for now).
I’m sure Intel will update their drivers before Windows 7 reaches General Availability.