I once had a lefty Westbury LP-type guitar that a PO had installed a Kahler. I never bonded with the guitar because of the Kahler, but it worked just fine. I have no idea how much the PO had played the guitar post-install, and because I didn't really bond with the guitar I didn't play it much, but there were no problems that I noticed. Sold the guitar about two years ago, and talked to the new owner- he tells me it's his #1 guitar, and he's gigging with it, so it must be getting some use- he has no complaints. So, Kahlers seem to be perfectly good whammys, AFAIK.
Yeah, I'm a mod. But I'd rather be a rocker.