Presto is about to die
And Opera will run WebKit
Yes, Opera will soon be using WebKit as its rendering engine instead of the custom built Presto.
Now, for the average web developer that didn't bother testing on Opera (desktop and/or mobile, and/or mini) it will not change anything. For web developers that bothered, well, it will make things simpler.
But but... variety is good, right?
Well, actually, variety is good and bad at the same time. Opera's efforts toward their engine will now be directed towards WebKit, and will then be used by quite a few browsers: iOS's, Chrome and Safari (hopefully Android's default browser will eventually die and be replaced by Chrome so I won't count it.)
Thanks to all the folks at Opera working on Presto for the past 15 years. I'm sure the future will hold lots of great stuff for you guys.