It seems people who have read the Silmarillion either love it or hate it. There seems to be no middle ground. Me, I love it. I read it when I was 13 or 14, and it just changed the way I look at the world. Heck, I've wanted to be one of the Noldor ever since!
One thing that bothers me for some reason is the "new canon" which was revealed in the Histories of Middle Earth series, specifically changing the parentage of Orodreth and Gil Galad. I'm on record stating that canon is overrated, but this one sticks in my craw. I think it's probably because the Silmarillion has been such a big part of my life that changing it doesn't sit well for me. So I'm going to keep it as my canon, later writings notwithstanding.
I don't want to leave the impression that I dislike the Histories series. I actually do like them, although I don't have the entire set just yet. I remember going to a bookstore asking if the store had The Lays of Beleriand. The clerk thought I was looking for some weird porn!