I have been building and editing corridors this afternoon. I LOVE the 2X faster corridor builds. Whereas in the past I would store up some edits and rebuild in order to be efficient. I have been rebuilding (applying) edits one at a time. Because of the fact that Civil 3D 2007 Service Pack 3 corridor rebuilds are at least twice as fast (sometimes more) I have been seeing my edits quicker.
This particular corridor is about 1,300 feet of rehab work (sawcutting and widening in a very irregular way).
Autodesk, a BIG thumbs up for this.