If you check the
Consolidated Lists, they now have the new material for Forge of War (abbreviated FW there) up. There are no new invocations, feats, base or prestige classes. The lists do not include any spells apart from Spell Compendium and Player's Handbook anyway, so there is nothing to be found out there (there seem to be new spells, though). However, there are five new monsters listed:
Arcane Ballista (Large Construct, CR5)
Karrnathi Dread Marshal (Medium Undead, CR 5)
Mistling (Fey, Template, CR varies)
Umbral Spy (Small Construct, CR 3)
Wargorged Raptor (Large Construct, CR 8)
Regarding the previews (finally!), I liked the description of 971 YK. There are some very interesting bits in there, especially the fact that Cyre managed to kill the Karrnathi crown prince and fatally injure the king. They seem to be going about this in an almost annalistic way, though through page-constraints I assume they didn't get every year of the war in.
I'm also interested in how far the Shadow War is developped. They seem to bring in some new items, and I also like the idea of the houses sabotaging each other (especially Orien and Lyrandar, it would seem). I'm hoping there are some more details on that.
A system for scars, both physical and emotional (shell-shock?) seems interesting as well, though so far we know nothing of that beyond the existence. I'm really looking forward to this books, and the previews on the page. And I'm hoping that they did not leave out the small nations (more on the Eldeen revolt, please!).
Shifting maps will be great too. Though I hope they won't start out with the one in PGtE, where Thrane's capital of the time (Daskaran; the map is ca. 500 YK) is in Aundair...
And "national takes on who betrayed who". Just what I like for my Eberron!