This is what I expected to see in TFA, rather than an introduction to Observer.
Don't get me wrong, Observer's really, really _useful_ and all, but -unless you're rather familiar with the syntax for the Erlang tracing infrastructure- it's... somewhere between challenging and impossible-due-to-impracticality... to use Observer to watch messages as they flow through your system.
benwilson, I wonder if the folks who wrote TFA would be interested in hearing about visualixir.