I can only add that Jon is right about the locking nuts. My experience is that if you do have a locking nut then the locking tuners are not necessary.
Further, and this is just my opinion, but having played a boat-load of guitars with and without locking tuners, if you are properly stringing your guitar then you don't really need locking tuners unless you are using a whammy bar a lot with a traditional nut. But even then, you still have the problem of nut friction.
Any good tuners will work fine if you install your strings properly. And Sperzels weigh a lot relatively speaking, increasing the mass of the headstock. I could tell a difference on my Strat when I put them on. http://shredlikehell.com http://guitarsoc.homestead.com