Thanee
First Post
We use pretty much only WotC books, but that's certainly not because the 3rd party publishers are seen as bad or something, it's just that we simply do not have (m)any books besides WotC stuff and that's certainly more than enough already. 
When looking at other companies publishing d20 (or other RPG) books, I mostly look for different and unique games, like World of Warcraft, Mutants & Masterminds or The Game of Thrones, which I bought recently. I will also very likely pick up the Warhammer 2nd Edition book eventually, and am waiting for my Shadowrun 4th Edition copy to arrive.
Bye
Thanee

When looking at other companies publishing d20 (or other RPG) books, I mostly look for different and unique games, like World of Warcraft, Mutants & Masterminds or The Game of Thrones, which I bought recently. I will also very likely pick up the Warhammer 2nd Edition book eventually, and am waiting for my Shadowrun 4th Edition copy to arrive.

Bye
Thanee