I've used them before, on many vehicles, including my current LJ on 35s before getting the black magic super 16s. They are slightly better than other brakes I'd say, but not too much. Big problem was that they don't do well without at least a little heat in them, so the first stop can be a wee bit scary, as they just won't bite. So seriously, keep that in mind.
Regardless, what you really need is bigger brakes. Worth every penny, honestly was one if the best mods I've ever done to any vehicle ever. Best only to use them while waiting for Mr Blaine to ship out your BBK.