The new one with 1.5 is ANNOYING, Yes I know it's the default gtk one these days but it's crap, slow and evil.
Here's how to disable it and get back the old one
The last post.
In Debian testing it's here:
/usr/lib/firefox/components/nsFilePicker.js
I even gave it a +i attr so it won't be overwritten when I get a new FF deb.