Yes, well the most common question surrounding kenpo has to do with whether or not the techniques could be pulled off against a non-compliant opponent.
Personally, I think the interesting thing is that Ed Parker--who had learned Kenpo earlier in his life in Hawaii--modified the style significantly based upon his own real-world fighting experience. Like Bruce Lee, he was known to get into tussles on the street and he developed his "American Kenpo Karate" to be effective based upon his real-world encounters.
In the beginning it looked a lot more linear and karate-like, but as time went on he added in a lot more kung fu-based circular movements and he built the techs to flow according to the natural movement of the human body.
Recently, Jeff Speakman--the guy who starred in The Perfect Weapon--further modified the Kenpo that he learned from Parker to account for boxing-style punches and he also added in some SD oriented submission grappling.
Personally, Kenpo is fascinating to me. I'm not sure how realistic it is, but I'd like to learn it one day if only because there is such an interesting history behind it and the theory behind the system is compelling.