Summary: The case looks like it's made of plastic. The knob looks especially cheap. From the photos I thought it might all be metal. The technical info doesn't specify, but someone wrote in a comment that it's made of MDF. I'm a bit disappointed in the presentation. For this price point, the knob is especially disappointing.
Summary: First, the obvious and most important claim: The sound IS all it is praised to be. I purchased the N22 through Crutchfield in March 2012 along with a pair of Infinity 153 bookshelf speakers to drive my computer desktop audio (primarily CD-to-FLAC source), and have since added a pair of Grado headphones to my desktop experience.
Summary: I use this amp to drive a pair of NHT SuperOne speakers at my computer desk and it works well. I'm very happy with the sound quality. I have my iphone connected to the RCA inputs and my computer connected to the mini-jack input. I do, however, have a couple of nit-picks. One is that the USB port does not charge either of my iphones. When I plug the phone into the port I get a message on the phone that says "Charging is not supported with this accessory".