Should I feel bad about leaving out the -khtml- prefix from css attributes like border-radius and box-shadow?
What is the percentage of Konqueror users anyway?
If the browser does not even show in your stats and your "other" browser listing isn't 30% or something significant, I think you can safely leave it out.
(And "other" is so low on StatsCounter that it barely registers. http://gs.statcounter.com/)