you will be allowed to start unsigned drivers on windows vista according to http://download.microsoft.com/download/9/c/5/9c5b2167-8017-4bae-9fde-d599bac8184a/x64KMSigning.doc
theres a discussion about it on woodmann http://www.woodmann.net/forum/showthread.php?t=7748&highlight=vista
but nevertheless drivers in freeware apps will become a problem if they are not signed cause the average user wont boot with F8 to use these apps