I got into this at Hypericon with Joe Lansdale. He hates 'em with a passion. Me, I think they're a tool. Used well, it gives (as you said) additional clues to the character and the situation. Used badly (you can't hiss a word, much less a sentence unless you're a snake, and even then only if you're using sibilants, damn it!) and they're, well, Bad.

IME(ditorial)O and R(eader)MMV

(edited,as usual, for typos)