I've got one of these on my Eddy.
Dunno if it's the Milltek downpipe combined with the Catback, but mine is very quiet - but quite purposeful on tickover and sounds definitely better than standard.
However when on 'full beans' there's a definite roar from the rear, it suits me that the only time it's roaring a bit is on full throttle. That's exactly what I wanted.