I built a lot of kitchens since 1976 until I packed that in 5+ years ago....2003, wow, that's 8 years ago...*shakes head* The bulk of them, we built with 120gram melamine over HD particle board. Trust me when I tell you that there are a LOT of different grades of PB and thicknesses of melamine. Sink cabinets were invariably constructed of plywood for all the reasons the rest of the guys here talk about. The 120gPB I used was not much of a cost savings over plywood, but so much easier to cut accurately, no finishing, certainly flatter and more of a consistent thickness. All said and done, the bulk of the cost saving by using 120gPB was in the fact that a single pass through the edgebander did the job. No face frame to deal with, No sanding, and 3 coats of spraying. The nicest thing about PB is that it is flat. The guys who bought the shop back then now use a lot of water resistant MDF of which Swing speaketh. Also available with 120g of Melamine.
If done right, there's nothing wrong with a quality heavy duty particle board.
Now we get to the crux of the matter: I like plywood except it is harder to be competitive in the marketplace from a price standpoint. In terms of look-and-feel? Nothing to talk about.