Positives: Print quality compares well with other printers in its class. Very large gamut. Easy to get a good print-to-screen match with the HP papers. Very long print life according to Wilhelm research. Fairly frugal with ink, even with the regular "self-testing" cycles. Cheap extended warranty from HP.
Negatives: See Cliff's review regarding wheel marks and paper banding. I'll add that for me, the wheel marks have only been a disappointment on the glossy paper. The bronzing and gloss differential are so bad on the HP glossy though, that I don't use it anyway. I've not had as much trouble with banding. It is just a once-in-a-while kind of thing; usually at the end of a very large, expensive sheet of paper! Ok, so I'm kidding on that (sort of).
Other gripes: The printer was released almost a year ago, but HP has only just recently provided driver updates. Unfortunately, my attempts to install many of these updates result in a "not intended for this printer" error message! HP has also updated the on-board software since the printer's release, but HP has never offered an update for us "early adopters" so I am stuck with minor, but annoying problems like a printer that often locks up when I open the media door. (Workaround is to hit the "OK" button first--wakey, wakey Mr. printer--sheesh!)
Papers: For me, image quality is the most important factor in choosing a paper (or printer). That said, the best paper for me so far has been the HP Advanced Satin. (I print mainly in color.) I don't care much for the "feel" of it, but you don't feel prints hanging on a wall. Color and tonal range is very good with this paper. It is also a good match for the HP Advanced Glossy which I buy cheap locally, then use as a proofing paper. I've tried a variety of matte papers, but a big drawback of many is that the feed/hold-down mechanism of this printer causes abrasion of the surface. Perhaps there is a fix for this that I've not found.
I hear the HP Professional Satin paper is also good, but I've not tried it.
Mark