use of Priority vs Conformance Levels

It seems that the WCAG WG, in their recently published Working Draft of Web 
Content Accessibility Guidelines 
(http://www.w3.org/TR/2002/WD-WCAG20-20020822/) has changed their 
conformance criteria - from using Priorities to using Levels (Minimum, 
Level 2, Level 3).   As stated, the WCAG improvements include: Ensure that 
requirements may be applied across technologies, Ensure that the 
conformance requirements are clear, Ensure that the deliverables are easy 
to use

We may want to:
1.  learn from them, why the change.
2.  review our use of Priority 1,2,3.

regards
Lynne