On the Opera move to Webkit again, I echo Jake Archibald's passage below.
I develop in Chrome, then check stuff in Safari & Firefox. Usually, this would be painless, everything would be as expected (usually). Testing in IE and Opera was often less fun. But here’s the difference, things would be wrong in IE because of bugs, whereas things would be wrong in Opera because they were adhering to the spec (I’m generalising, of course).
When Opera did the wrong thing with appcache FALLBACK entries I poured over the spec for a couple of hours on the assumption they were doing it right and the others were doing it wrong. Turns out Opera had a bug, but if any other browser was behaving so differently I’d have instantly assumed it was that browser getting it wrong.
Jake Archibald: on Google+
Presto, you'll be sadly missed.