Psion
Adventurer
In response to Psion's request, I'll comment.
I've been DMing D&D for less than a year, and GMed a little Star Wars before that (maybe a year's worth). I am mostly running the game because we needed somone to run it, and I have a good job and can afford supplements and such. Anyhow, because of time constraints I only run published adventures, with the occasional random encounter created by myself or from outside sources (En Route rocks). My players are mostly the kick in the door, kill the orc, disable the trap get the gold and XP type, with a wee bit of roleplaying thrown in with the purpose of making the above easier.
Okay now you have background on my campaign, here's my policy on "Official".
I typically let players use anything they can purchase off the shelves or PDF's. Why? Because they spent money. I've been burned buying stuff and never being able to use it, and I would hate to do that to someone else. Most of my players don't have full-time jobs, and buying a book is a big deal. Also they usually check with me or even ask my recommendation before buying. I do reserve the right to step in and disallow something that is blatantly overpowered.
Cool... thanks for the feedback. It sounds as if you have a healthy policy balancing the need for some stability in the rules with allowing additional resources.