Opera has announced its next browsers will use the open-source WebKit rendering engine first developed by Apple from the KHTML code base when Apple launched Safari (version 1.0 dates to 2003).
The benefit of standards on consumer product choice and the ability of different vendors to compete on features (as opposed to compatibility with undocumented file formats) is a theme previously hit on here. The upside of WebKit is that it allows multiple vendors – now providing the majority of web users with their browser of choice, a rather different situation than depicted not long ago by Microsoft's Steve Ballmer – to share the burden of a high-performance standards-compliant code base, while focusing on other areas of development for differentiating features. By promoting standards, we allow users choice by lowering the barriers of lock-in caused by common but ill-documented products previously targeted on the Internet.
Remember the old notices to come back with a different browser? Or that a site looks best on some browser you don't want to use? Or those messages generated by servers that sniff your browser agent-string to determine that you aren't using the browser distributed by the vendor of the site developer's web design tools, and send you bogus error messages claiming your browser is incompatible – without even bothering to send you the page to see if it is or not? And how you used to rig your browser to LIE about its identity so other browsers would treat it like "one of the gang" and send the real content, which it displayed error-free despite the bogus warnings sent by the crooks trying to control your browser choice?
No? Well, it wasn't that long ago. If you can't remember it, be thankful for things like WebKit. Without its ubiquity, smartphones wouldn't have the wonderful access they now enjoy to the Web.
Without crashing. And for a look at how different browsers can be while using the same rendering engine, consider Google's Chrome.
Now, go back to the rest of the web :-)