So, as the OP said - back to the bad old days of IE6 dominance.
I was doing some webdev back then, and whilst everything you said was true it was the lack of cross browser CSS and Javascript testing which led to the real frustration.
Back in 2002/03 IE6 had over 90% marketshare, and justifying testing in anything else was a constant battle.
That's exactly the same situation with Chrome. It's faster than Firefox, has less CPU issues etc (and I say that as a long time Firefox user).
The mono-culture is the problem, and it's embarrassing that we've forgotten this.