I've owned both. Nothing wrong with Leupolds as long as you've got the bucks. Burris FFIIs are comperable in clarity, design, and function for a lot less money. I've never had any problems with mine and I can't say as I know anyone that has. As far as warranty work Leupold has a great reputation. I have heard only of a couple of issues with Burris? Can't go wrong for the money.
Cheers