I received several great questions at the MSDN Events last week, and 3 that I could not immediately answer. I have found some information to address two of them (see below) and will append what I discover about the other 1 shortly.
Q. What does manual checklist do in the Accessibility section of the ASP.NET 2.0 website property pages?
A. First off, there is a handy walk-through on beta.asp.net for Creating an Accessible Web Application that I recommend. Secondly, I played around with the accessibility tools and discovered that a) I don't know how to force an "accessibility error" in design-mode and b) the manual checklist option produces a checklist of WCAG guidelines to follow when producing web applications.
Q. Is there a way to apply default control properties to multiple control types simultaneously in a .skin file?
A. None that I could discover. If you have several control types that will share common property values (e.g. label, textbox and button all have the same backcolor), you need to declare each control type individually in your .skin files. When you consider the capability to override skin definitions using the skinId property, the requirement of explicit declaration makes sense as it aids you in creating multiple types of each control when you seek that functionality.
Q. Are there plans to improve the design-time rendering of ASP.NET pages that utilize themes declared globally in the web.config file?
A. Jury is still out...