I love the filtering and have already suggested a few things to add.
Well I could be missing something but it would be usefull that if you drag an icon / file to another fence then the filtering for that icon / file should be turned off so that it will stay in the fence you have just put it in.
E.G. I have a fence that puts all downloaded exe files into Exe files. However if I then want to move one of these files to say a fence called "Keep" it will not allow you to do so as it just puts it straight back into the exe files fence. I would like to be able to put it in the keep fence and not get it filtered.