I got an HD300 two weeks ago and have been really impressed with the sound quality. Leagues better that the XT (which itself was a great modeler in its time) or even Amplitube and AmpKit.

The supplied DC-3G power adapter gives me cause for concern, though. I noticed that it produces a rattling sound when shaken along the axis of the contact prongs. Just wanted to ask other DC-3G/HD300 owners engineers whether this is normal or if there's something loose in my unit that can cause malfunction or failure later (possibly taking out the HD300 when it conks out).