Mine arrived today.
Lots of good advice for newbie DMs, from which even old hands can still pick out some new insights.
Some stuff is more how-to for the newbie, like how to draw up a quick and dirty battle-mat, or how to use miniatures to help set the scene.
Best bits: Advice on managing your game and managing a campaign. Magical Locations as treasure. Guild/Organization rules. Fully-detailed City of Saltmarsh (of 35 or so pages, 32 are the locations; the other 3 are the basics of the city population). Mentoring and Apprenticeship rules. "Archetypal" encounter locations (burning building, ice bridge, lava pool, etc.) and special rules they might need. And quite a few more.
Bad bits: Not many. Nothing is perfect, but not a lot to complain about here.
While I like the sample Complex NPCs, and the new Stat-block format (as presented in Dungeon recently), I do wish the sample NPCs had a level-by-level progression. The utility of the sample NPCs in the main DMG is that there is an entry for every level, Need a CR10 Fighter ? There's one in the DMG (very generic, but acceptable in a pinch). Need a CR4 newcomer to a cult ? Well, there's a CR 6 cultist.. you can back out a couple of levels to get down to CR 4.
Of course, I realize that the nature of the Complex NPC beast does not lend itself to the same level-by-level progression, but maybe some guidelines on building a Complex NPC out of the generic simple ones in the DMG would have been helpful, in the "give a man a fish and he will eat today/teach a man to fish and he will eat again and again" sense.
Paper Quality ? Not something I worry about. Feels good, nice and smooth, enough weight to feel "substantial".