I have fitted one as well........... I agree with GGTTRR the Willall Pipe sounds awesome under power, however, I would have to say there is a bit of drone around 2k rpm when you are using partial throttle (more so when you are in 4th, 5th or 6th).
Still when you hear the sound it makes when you are changing down though the gears (with the blip) nothing much else matters.
I wuold fit it (really quick job) and try it, you can alwasy replace with oem if you don't like it.
And no I won't be pulling mine off
Cheers
Mark