Funny, my only complaint about Toronto was that the immigration officials tried hard enough to avoid charging me the work permit fee that it wasted a bunch of our time.
Best experiences though have been Singapore and Kuala Lumpur. Worst experiences have been Houston and JFK NYC. Sea-Tac is ok aside from the body scanners.
I was surprised to find that leaving Tegel in Berlin was easy as can be, short lines, quick trip through the metal detector. The entry process at Sea-Tac was another story though. It took forever. You got grilled, you got the German Shepherd dog sniffing your crotch, and you had to wait for all your bags to be x-rayed. Some of the agents seemed to be behaving in a very rude way, in particular I remember one agent seemingly being a real jerk to some poor old guy who didn't speak English well. I remember thinking how bad an impression of the US that the foreign visitors in line must be forming. I was at that moment embarrassed to be a citizen.
[edit: %s/x-ray/metal detector/]
I'm kind of scratching my head here, because that doesn't jive with my experiences (and I do have plenty of experience of entering Canada there as a non-Canadian -- in fact, I've done it twice in the past month). Some times of day the lines are a bit longer than others, but I just don't know of anything else that I'd consider to be bad about it.
I've since decided not to fly into North America via Toronto from now on it was so bad.
I dearly love my Canadian neighbors so I hope they've since straightened it out.
The funny thing is, in CDG, what was bad was the immigration exit control. Entry was a breeze and I was asked exactly zero questions even having presented a non-EU passport.
One time I think I timed it at around 2 and a half hours to get processed. No particular questions, just the usual look at the passport, look at you, stamp off you go. But there were probably a thousand people passing through the control point.
Schiphol, El Prat, Marco Polo, Dublin, da Vinci, Kloten and Munich get me in and out without any fuss at all. Though security at Schiphol was about what you'd contend with at Dulles.
Domodedovo and Koltsovo are very mediocre and busy, but function. You might get harassed by security, you might not. Who knows? It's Russia after all.
Kuwait was easy-in easy-out, but basic airport services were generally a mess, due mostly to rampant queue hopping that none of the employees put a stop to.
My consistent best anywhere is traveling to South Korea. I would replace every airport on the planet with Inchon Int'l if I could.
In the U.S. Washington DC-Dulles and Denver are pretty smooth operations most days, JFK and LaGuardia are crowded but function and security doesn't really harass you, Charleston, SC is one of the easiest to get in and out of (even internationally). San Francisco, Sea-Tac and Portland are..."alright". LAX kinda sucks. O'Hare is a nightmare almost on the scale of Heathrow and Atlanta is a mess most days with what must be strictest security on the planet.