What more needs to be said about the greatness of Rappan Athuk?
I own it in 3.5, Pathfinder, and 5th Edition now, with the latter products now including the products being reviewed here.
While I've not had the chance to run all of the new additions to the Dungeon of Graves, I can say that a few of the new additions (such as Castle Calaelan and the Tunnels of Terror) are fantastic additions that allow your lower level PCs a taste of what lurks beneath without necessarily being fed directly into the meatgrinder.
Regardless of the level, everything added feels like it fits seamlessly into the overarching lore and sense of impending doom that pervades Rappan Athuk. If you're running the game in this edition, these are an invaluable way to extend the game to include lower levels while also adding in some nasty surprises for your higher level team.
[5 of 5 Stars!]