Every so often, I go around the Wizards boards looking for information from the actual Game Designers. Mostly I look for miniature information (and compile that on my webpage), but I do look for more general D&D info as well.
Here's a bunch of posts made by Andy Collins over the past few months.
The Medium Save Progession
Querent - The Medium save was invented a long time ago, and it seems WotC didn't have fractional progressions in mind when they did so.
Andy Collins: As the person who created the Medium save progression for Star Wars when I was still a neophyte designer, I can say that's pretty much dead-on accurate. The design team wanted something between the polar extremes of "Good" and "Poor" saves, and that progression split the difference.
I remember, some time after I created the progression, Jonathan Tweet asked me what formula I'd used to build it. After I stared blankly at him for a few seconds, he realized that the 3E designers *hadn't ever told anyone* that there was a formula hiding behind the good & bad save progressions.
http://boards1.wizards.com/showthread.php?s=&postid=3635938#post3635938
(I love that one. All the great design philosophy of 3E unravels if the basics aren't explained! I felt that about monster design - thankfully the 3.5E MM makes it much clearer - MB).
Libris Mortis Information
Querent - October is so far away, sigh. I wish Collins or Cordell would be so kind as to give us a tidbit, just a tiny morsel from the book?
Andy Collins: Do you mean something like "DMs can look forward to getting full game statistics for dozens of sample undead using the templates from the Monster Manual, making it super-easy to drop a bunch of cool zombies or a nasty vampire into their campaign"?
Does that qualify as a morsel?
Querent - Well yeah Andy but is there stuff about Deities that favor undead in there too?
Andy Collins: The original request was for "a" morsel, so that's all yer gettin' from me.
http://boards1.wizards.com/showthread.php?s=&postid=3651361#post3651361
(A frequent poster on ENworld is the Querent!)
Subsitution Levels in the Planar Handbook:
Andy Collins: The sub levels in Planar Handbook represent our "first shot" at this new mechanic. They don't always hit the mark we were aiming at, but overall I think they represent an exciting new option for players to explore (and one we'll continue to explore in the future...).
http://boards1.wizards.com/showthread.php?s=&postid=3942789#post3942789
Planar Domains:
Andy Collins: I'm glad you like the planar domains.
It's true that we could have done more, but we felt the list there was enough to get players & DMs started.
Wouldn't surprise me if someone made the effort to write up more in the future, but it probably won't be in a Wizards D&D product unless/until we revisit the planes specifically.
http://boards1.wizards.com/showthread.php?s=&postid=3935151#post3935151
Cheers!
Here's a bunch of posts made by Andy Collins over the past few months.
The Medium Save Progession
Querent - The Medium save was invented a long time ago, and it seems WotC didn't have fractional progressions in mind when they did so.
Andy Collins: As the person who created the Medium save progression for Star Wars when I was still a neophyte designer, I can say that's pretty much dead-on accurate. The design team wanted something between the polar extremes of "Good" and "Poor" saves, and that progression split the difference.
I remember, some time after I created the progression, Jonathan Tweet asked me what formula I'd used to build it. After I stared blankly at him for a few seconds, he realized that the 3E designers *hadn't ever told anyone* that there was a formula hiding behind the good & bad save progressions.
http://boards1.wizards.com/showthread.php?s=&postid=3635938#post3635938
(I love that one. All the great design philosophy of 3E unravels if the basics aren't explained! I felt that about monster design - thankfully the 3.5E MM makes it much clearer - MB).
Libris Mortis Information
Querent - October is so far away, sigh. I wish Collins or Cordell would be so kind as to give us a tidbit, just a tiny morsel from the book?
Andy Collins: Do you mean something like "DMs can look forward to getting full game statistics for dozens of sample undead using the templates from the Monster Manual, making it super-easy to drop a bunch of cool zombies or a nasty vampire into their campaign"?
Does that qualify as a morsel?
Querent - Well yeah Andy but is there stuff about Deities that favor undead in there too?
Andy Collins: The original request was for "a" morsel, so that's all yer gettin' from me.

http://boards1.wizards.com/showthread.php?s=&postid=3651361#post3651361
(A frequent poster on ENworld is the Querent!)
Subsitution Levels in the Planar Handbook:
Andy Collins: The sub levels in Planar Handbook represent our "first shot" at this new mechanic. They don't always hit the mark we were aiming at, but overall I think they represent an exciting new option for players to explore (and one we'll continue to explore in the future...).
http://boards1.wizards.com/showthread.php?s=&postid=3942789#post3942789
Planar Domains:
Andy Collins: I'm glad you like the planar domains.
It's true that we could have done more, but we felt the list there was enough to get players & DMs started.
Wouldn't surprise me if someone made the effort to write up more in the future, but it probably won't be in a Wizards D&D product unless/until we revisit the planes specifically.
http://boards1.wizards.com/showthread.php?s=&postid=3935151#post3935151
Cheers!