I just read Daring Fireball's short so-called « analysis » of the Opera switch to WebKit. Even I perfectly know that guy is almost only an Apple PR guy, I'm again surprised by his limited ability to analyse a situation. The only question that is worth it is the following one: whatever is the strategic rationale that led to that choice, it's obvious Opera had the choice between open-sourcing Presto to build a larger community around it and ditching it in favor of an already open-sourced rendering engine. So why did they choose the latter?
And in terms of WebKit better than Presto, well, Opera has always been a better player with respect to standards than Apple. As many people have already said, a test failing in Presto was often the sign the test was wrong or the spec had a problem, given their extreme adherence to specifications.
So as usual, you can avoid reading Daring Fireball. No hyperlink from here. Nothing to see there.