1: How long have you been in the hobby?
Depends on your definition of into the hobby. I have been playing since about the start of third edition, twelve or thirteen years now. However, I was first introduced to all of this back in '98 with chaos gate and final liberation. Loved those games, still no walk in the park either.
2: How important is Fluff to you, relative to other aspects of the hobby?
Fluff is the major player in the hobby for me; I like list building because I have a thing for numbers but the stories and background are what truly draw me in and keep me going. This is especially so for the works of many authors, both employed by GW and Black Library and those who write their own stuff and know how to do it very well.
I don't play so much these days, midway through high school many of the local shops closed up and in college many of the local players are the asshat type of competitive. They do more harm than good to the hobby in my experience, so the fluff is a big thing for me.
3: How devoted are you to the works of the Black Library? By this I basically mean what compels you to buy/read one of their novels, do you pick them because of the races involved, follow certain serials, on a whim, etc...
For the most part...no I have absolutely no preferences when it comes to Black Library works. I do tend to favour some of the more out there, older, or off beat works like the Inquisition War, Sons of Dorn, or the later Space Wolf books (honestly, I bought and finished Wolf's Honour in like three hours and was left wanting more, never did that for any of the ones King came out with.)
4: How many codexes have you taken the time to read thoroughly, including older editions?
Don't know, more than I might care to admit; I have a lot of them and I really don't want to get counting.
5: Do you enjoy postiulating theories, pondering mysteries, and writing your own works to expand your enjoyment of the hobby?
From time to time yes, going beyond the drawing board and onto the writing of whole stories is something I tend to struggle with (shorter bouts are easier for me) but I do try now and then.
I do like to help people with their own work, because I have a fair depth of the fluff; though fairly often this looks like I am just tearing people's work apart. Then again, if something isn't good or doesn't make sense, I am going to be honest so some people can just suck it.
6: If youa have anything further to add, feel free.
Have had Asylum by Disturbed for days now and loving every moment of it.
Also, for those of you who have not, give a browsing through the original works section. Some of the people there are extremely talented and come out with great works.