One aspect which drives me nuts about using Siri in public, is her inability to match my own volume. Often I'm in a relatively quiet office, or somewhere else where shouting would be inappropriate. I bring the phone close to my mouth and speak my command softly.

At the loudest volume setting, Siri replies "ALRIGHT, STEPHEN, I'LL REMIND YOU TO WHATEVER WHATEVER".

The one feature that would get me to use Siri more is if she would speak more quietly!