ARGH, definitely. Most of the time I'm able to just say "eh, no one really cares" and work my way through the block, but comedic timing is one of those things that stuttering completely messes up. I deal with it by using a type of humor that relies on long, drawn-out pauses, facial expressions, etc . . . a raised eyebrow can go a long way. But sometimes I'll watch comedians who rely on David Tennant-style super fast speech, and get bummed out.