[drostie]

Well, it depends what you're writing. One of the horrible things about early fiction is that the writers usually insert their own interpretations of how characters talk -- including stuttering and "ums" and whatnot. Thankfully much of this is wasted on fanfic, where you know what the author was trying to emulate -- but usually it's a distraction. Great characters can get by without habits written into their dialogue.

[drx]

Characters with speech habits are not necessarily a bad thing -- http://tvtropes.org/pmwiki/pmwiki.php/Main/BuffySpeak (warning: tvtropes link)