I listen to a lot of technical shred guitarists, Vai, Satriani, MacAlpine etc. To my ear, there's something odd & sterile about the midrange tone on a locking guitar, somewhere between about 1.6K to 4K. It's more noticeable to me on the cleaner, softer stuff. I think Joe Satriani gets the greatest variety of tones among those locking-whammy guys, but compare the very best of his clean tones on "Surfing with the Alien" or "Crystal Palace" (my favorite of his) to the clean tones from Eric Johnson, Steve Morse, Andy Timmons and other bolt-neck but non-locking guitarists.
Of course tone is a subjective thing, and the Floyd Rose metallicism has enter the culture as perfectly acceptable - I still listen to these guys. However, the use of Floyds & Ibanez Edges & Lo-Pros would be nearly universal if there weren't some downsides to using them, I think - they sure do stay in tune. A lot of great guitarists like Timmons, John Petrucci, and Paul Gilbert have reverted back from using locking whammys, and they cite tone as the reason.