One of the evils of guitar tremolos is the reliance on springs to return the tremolo to its neutral position.  These springs essentially operate like a combo amp reverb tank built inside your guitar — they ring when physically excited.  Skeptical?  Strum some full chords followed by a quick palm mute and you’ll hear those springs ringing.  The ringing can add a boingy or hazy quality to your tone, masking the qualities you want to hear.  As you increase gain from clean to distortion, the ringing in amplified through your pickups and can become quite noticeable and annoying.