Neo said:
Lets see...
Which one of your creations do you yourself consider your greatest work?
Who of the new batch of creative whizz's would you most like to work with?
Is there a product for d20 that someone else did, that you wished you had created yourself?
Can we clone you to ensure future generations fo Gamers get to enjoy your work as much as we have? 
What one thing would you have done differently in your career looking back now in hindsight?
What advice would you give to aspiring freelancers?
What genre or specific setting that is out there, would you most like to see converted to D20?
What piece of advice would you give to Wizards regarding thier approach to D20 and its marketing as a longterm gamer and creator?
Erm there you go off the top of my noggin....
Okay, and that's quite a laundry list
As with children, picking favorites is not my style. I can say that I had a lot of fun writing all the RPGs that I've done, and that the modules are a lot of work but they too were enjoyable. In all, I have a number of historical games that I really like a lot and would love to see published and played. Think of it this way: I am a hardcore gamer, and I like to create and play games. The project I am working on or the game I am playing at the moment is the *current* favorite.
As for working with co-writers, and I have worked with quite a few, familiarity is a key factor. That said, I find that working with Jon Creffield of late is indeed very much a pleasure.
It is not possible for me to produce as much as I do and spend a lot of time reviewing other author's work, so I can't comment. Fact is I don't get the time I wish I could to read fiction. Not all work and no play, but close...
As for cloning, heh! I'd do that now to get to more of the ideas I have were it possible. What I hope will happen, though, is that some of the gamers who have read and played my material, or who have worked with me in creating such work, will come to the fore in due course with their own excellent work, some of which will possibly reflect some of my style.
As noted, I dn't spend time or energy tinking about the past, what could have been changed. However, I try not to make the same mistakes over and over...
Aspring freelancers: Work for love, not money. If you enjoy the effort, love gaming, then that will cme through in your writing. To break into the field, figure on a lot of material being published on a gratis basis, and be sure yo produce plenty to as yo become known. Writing modules for convention tournament play is a great way of building a "name," of course.
No comment on D20 conversions, sorry.
As for advice to WotC. I don't think they need any in regards the D20 system. However, in regards to the new D&D one, I believe that there is a question of "legs" for many new players, because as things stand the game allows too rapid level increase. There's more, but if Hasbro wants consulting, they'll cntract for it
Gary