I've been working with Blaze since October '08. I think he was mostly used as a Western trail horse before I got him, and I ride him English. His owner's daughter shows/trains horses (and has given B and I lessons), and she suggested I get a full cheek snaffle for him. I have, and I'd say it works moderately well.
It's my personal opinion that he has somewhat of a hard mouth. He often tries to run through my hands (and I'm very aware of not hanging on his mouth) and will try and get his head down and brace against my hands. Does he a need a "harsher" bit? I toyed with the idea of getting a full cheek french link snaffle at first, but had an easier time finding a more affordable regular snaffle. He gets very rushy at some gaits and we're working on slowing things down (thinking legs to seat to hands to soften-THANK YOU HGS), but he barely acknowledges my half halts.