First, love the fences. Very usable and really helps organize the desktop. On the downside, at least on my system, if I have a fence that includes document files (.xlsx, .pptx, etc.) and I open and save the document the document itself jumps out of the fence and back on the desktop. I can, of course, drag it back in to the fence - but would love not having to do that.
Windows 7 beta if that makes a difference.