If a few people use it, I'll keep it enabled. If no one uses it, I'll drop it and it ought to speed up page load time on threads for dial-up users a fraction.
I almost invariably use the quick reply - very useful as the earlier posts stay in view so it is easier to reply to several points in turn and still be able to refer back. So useful that (when wanted) I'll even type in the quote code rather than use the 'quote' button.
Another advantage of the quick reply - to return to the 'new posts' (or forum list, etc), one only has to click 'Back' once, instead of 3 times