Was thinking on this recently and was wondering about it mostly from the perspective of the 4e fans who claim that the encounter guidelines "work" in 4e. What does this mean? What is the criteria being used to determine this? Is a challenging encounter usually "challenging"? If so how do you relate this descriptor to what actually happens in an encounter? Same for easy and hard as well.

On the other hand I would also be interested in hearing from those for which the guidelines don't work and why that is... In general is a hard encounter usually a cakewalk? Is challenging too easy? How do you view the descriptors of easy/challenging/hard and do 4e's encounter guidelines fall in line or outside of what you picture these descriptors as representing?