In addition to my last post on this issue here, Windows 7 Service Pack 1 has brought with it only a minor change. The details in that post are still valid, with one minor exception.
In "Stage Two Prepare the WinPE Image" I referred to a hot fix package KB972831, which contained the WinPE module for 802.1x. This had to be added using DISM /add-package. Happily the Service Pack 1 AIK toolkit now contains the winpe-dot3svc.cab in the same location as the other three cabs (winpe-scripting.cab, winpe-wmi.cab, winpe-wds-tools.cab.)
This means that there is very little reconfiguration needed for introducing your SP1 image.