Well worth it, and I don't even play Pathfinder.
I so want to play this game - I have almost all the the original books - but no one in the rural hell where I live plays RPGs, let alone with a 57-year-old geek.
There are some good setting books in there too. The Freeport book by Green Ronin is great and you can easily strip the Pathfinderness out of it. The Kobold Press stuff is also great (it focuses on their Midgard setting) and has a wealth of great lore and ideas that can easily be de-Pathfindered as well. Well worth the $15 or more for all this stuff, even if it is Pathfinder. As Erik mentioned, Rappan Athuk was written for old school gaming and you can easily ignore the Pathfinder mechanics for any skill checks (I usually strip them out anyway because I want my players to describe how they are going about things) and swap in S&W critters from Monstrosities & Tome of Horrors Complete on a 1:1 basis.