the Lo-Pro Edge Vibrato in the Ibanez S540 is a fantastic unit (i own one S540), please do NOT replace it :wink:
so what's with a particular manifestation/ brand of a floating vibrato? it's all about reliability- does the vibrato bridge return your strings to pitch after use? this is the main concern.
thusfar, the Original Floyd Rose unit works very well. Ibanez's own interpretation of the Floyd, its Edge/ Lo-Pro Edge/ Edge Pro/ Edge Pro II/ III all work superbly.