Just wanted to chime in with some of my experience. I've had these, along with the Mistral crossover, for some 8K miles. I've run them with the baffles in originally, and had the bike dyno tuned with that setup. They were slightly louder than stock but not loud enough for my taste; I wanted more of the Guzzi sound. So the baffles went out and the bike was retuned on a dyno again. They sound raw and exciting, and, as some would undoubtedly claim, like a "real Guzzi should". That said, without the baffles they do make my bike rougher off-idle to about 3K+. From there and to the redline, however, it is all a bit livelier, like a veil has been pulled -- the bike seems to rev up easier.
Mine also do have that slight "whistle" on the overrun that Lucky Phil is reporting -- I think we're talking about the same thing -- but it can only really be heard at low speeds when coming to a stop, say. At first it sort of bugged me because it sounded to me like a mechanical rattle of sorts but once I realized it was air moving through pipes, I got used to it. I think what I'll do next is experiment with cutting down and modifying the baffles.
As far as luggage -- in the pic below you can see a set of Ventura bags that clear these pipes easily.