Ah yes, after that experience, I'll definitely do an additional layer of strategizing when I have trips to the US: how long to plan for connections, which flights to take, etc. If it weren't for good friends being in the US, I'd try to avoid trips there.

When the process works, it isn't too painful (the return interview took only an extra five to ten minutes of my time). But when things go wrong -- such as when they put your passport in the "wrong" pile , which was what happened with mine -- you can end up with long stretches of time, during which you'll have no meaningful way to get updates or plan contingencies. Bring a book (an iPod might prevent you from hearing your name being called out).

By the way, IME a secondary interview also meant a 100% chance that you'll be asked to open your luggage so that its contents can be searched by hand.