>>What happens to the signal when it hits the limiter? Is it audible<<
it's just compressed a little and not allowed to get any hotter. it's the same as running a soft limit on the minime or ad1000. it'll stop overs. you won't hear it if you run the levels correctly
if you run way to hot and rely on the mp2 limiter to keep it below clipping, then you'll hear it. too much compression can make the high end sound very harsh, but if you run it as usual and let the limiter stop the occasional overs, you'll be fine. hope i'm making sense.
basically it allows you to run a little hotter than you'd normally run at a stealth show because you know that any occasional overs that you might hit will be stopped from being overs.