I cut my teeth in the support department of the No-Name Software Company and dealt with a wide
variety of personalities on the other side of the
phone. Most of them can be filed into one of four buckets.
Nice-Smart: Rare unicorn. These people are truly a pleasure to work with no matter what the issue.
These people are nice to work with too but often you have to carry the
weight because they just don't understand what they are supposed to. On
the plus side, they are usually self-aware enough to know just how much
they don't know.
Smart-Mean: These people don't give an inch.
Dumb-Mean: Are really angry that they don't understand what you do.
Icarus Theorem of Scheduling: if you schedule two
people to visit your home (plumber, cable installer, electrican,
whatever) they will come at the opposite ends of their schedule window
such that you are trapped at home for the maximum amount of time.
Correllary to Icarus Theorem of Scheduling:
if the windows are different (morning and afternoon for instance) they
will come at the beginning of the first and the end of the second.
This theorem scales up in such as way as the more scheduled appointments the more chaos will ensue.