I don't really like the flick-fires. But like Don said, the kids do. If it adds more playability to a set, then it gives kids something else to do with it, which then gives them more reasons to want it. I wish LEGO could come up with a little better firing system for there sets, but the flick fires are cheap and work (sometimes), so I'm sure we'll be seeing them even more. I do like the spring loaded missle that LEGO has in some sets, like the newer Slave I, those shoot fare and work, but its to big to be put in smaller sets, so that were the flick fire comes in.
But since LEGO has rereleased the pirate line, the cannons have a fairly effective firing system. It would be nice to see LEGO format that type of firing system into the sets, but I doubt it will happen.