one thing that makes me crazy-- people who leave you a phone message at a perfectly reasonable speed but then say their phone number at top speeds.

If you are giving someone a number, you expect them to write it down. therefore you should speak slowly enough for them to write, and then repeat the number at an average speed so they can check it.

thus: "I'm at five fivefiveeighteight eightonesixonesix" and so on, followed by "that's 5.5.5.-8.8.8-1.6.1.6"

user-centeredness starts at home!