Saw this last night in IMAX 3D at 40fps. Fucking awesome. It's fun, tense, and looks fantastic. I wasn't too happy with the first one due to what I felt was padding to stretch it out into 3 movies. I don't mind them adding some of the stuff from the Simarillion or the appendices as they are part of Tolkien's world. The albino orc chasing them in the first was a bit much for me (as Thorin actually killed him in the battle). But the second movie made some of those decisions make sense.
I don't like that they shoehorned a female character into the center of the story just to have a strong female character in the center of the story. But I have to admit that it was handled better than Arwen in the LOTR trilogy. I wasn't too sure about Legolas having more than just a cameo either, but Jackson reminded us that he was a badass.
A good cast all the way around. Stephen Fry was brilliant. And it ended on the kind of cliffhanger that the Two Towers and the first one should have. The 3D was great. It wasn't just tacked on to throw shit at you. It created depth in the world and drew you into the film. Snow falling in 3D made it feel like you were in the middle of Laketown's square.
This movie is a must see in IMAX 3D if you get the chance. If not, well, you're fucked. Life has past you by and shit on you while doing it because God clearly hates you.

How much of the Simarillion was actually written by Tolkien?

I hear it was kind of a boring bastardization of his ideas part way through.

You heard wrong. It was essentially the history of Middle Earth that he used as a reference when writing. His son later edited and published it.

actually dain killed azog at the battle of nanduhirion if I recall correctly.

tolkien was very attached to the silmarillion but could never get publishers to pick it up. he actually briefly parted ways with allen and unwin to see if another british publisher would give the silmarillion a shot, but when that didn't happen he came back to A&U with snippets of what would become LotR, and the rest is history. the problem for tolkien was that the silmarillion never stopped evolving, to the point that no coherent drafts could be assembled during his lifetime (christopher tolkien's efforts compiling what we have today were nothing short of herculean if you read through histories of middle earth and track the numerous changes), and the problem for potential readers was that the scale of the thing was just immense and completely unlike anything else at the time.