One of the things I've been planning is to have my kick-ass dev team deliver a set of kick-ass whitepapers about Whidbey. Our doc people have really worked hard to deliver a much-improved set of documentation but there's lots of areas where even more technical detail can't hurt.
Soooo if you have areas that you'd like some more of this detail, let me know by leaving a comment with your idea and we'll make sure we add it to the list of candidates. Topics should be in the Windows Forms Runtime or Designtime domains...
Some examples:
Writing DataGridView custom columns
Writing ToolStrip custom renderers
Debugging performance issues in Windows Forms
Using the MaskedEditProvider in your code
Writing controls that support visual styles (XP Themes)
Etc...
Think about when you've been using the docs and have thought "gee, I wish this told me more about ____", that's probably a good idea. Let's hear 'em!