I determine what is and is not preferred the old fashioned way: I ask people. Around here and online, the vast majority of people don't like the 3.5 weapon size rules. Thus they are replaced with the 3.0 rules. After that it is a matter of playtesting and asking people to try out any changes, then making needed alterations.
So far I've not had any major complaints about the rules used or added material, and have managed to come up with solutions to all minor complaints.
As for the new psionics rules, I have had over a dozen people (three full game groups plus some individuals) go over them and try them. So far all the complains have been on the order of small balance tweaks and editing fixes. Even a couple guys who were fanatical about the WotC system, and said they would "be happy to tear apart your system", have decided to switch after trying it out.
So I'm not too worried about the reception of the new psionics rules or the various non-psi rules and material, since it has been overwhelmingly positive to date. If anythign it annoys me, since it is hard to improve without NEGATIVE feedback to know what to fix!
But in any case I'm not here to "pimp" the books. I'm here looking for help with art and fluff text, as well as suggestions for extra material. While I appreciate the desire to ask about the system itself, and enjoy answering questions about it, that is not the purpose of this topic