Graham,
I bypassed the internal unit altogether and bit the bullet for a VoiceLive Touch2. It gave me superior harmonies and the added routing to pump my guitar through the internal speakers ... something ELSE I was missing! Now, I can use the same vocal/guitar system whether I have a KB on the job, or not. I like that flexibility.

For really quiet, or short jobs, I can live with the internal processor ... I just don't like it.