Ouch - as Ash stated no fun.
Just remember that one thing I do like about screw drive lenses: the electronics are much less complicated than the VR/IS/OS lenses for Canon/Nikon. Any problems with a lens having this technology will cost a significant amount of money. Go check some of those brand specific forums as proof. I am not saying or implying anything by the previous sentences. It's just another consideration if something goes wrong, especially in terms of cost.
Grant: I like your analogy on the "mortgage"...
Regards,
Marc