I'm posting a reply because you didn't answer me but, this change of $sfile returning $null on reserved folder will break my scripts (and it should break all scripts which handle $null as a 'cancel' which is common since we have no way of knowing when the user canceled the dialog), it doesn't look like there is a need for this break of backward compatibility at all, where returning a different value such as -1 would be a much better idea.
