Opera has never gotten the sort of attention and respect it deserves, at least judging by its paltry market share in most parts of the world. But the browser has always been on the cutting edge when it comes to web technologies and standards.
The latest release, Opera 12, isn't as much about pushing the boundaries as it's keeping up with Firefox and Chrome, though there a couple of places where it's taking the lead, access to webcams for example.
64 bit builds on Windows and Mac
Opera 12 is the first Opera to be available in both 32-bit and 64-bit builds, which means you can run it natively on your Windows 64.
That won't mean much, for the average user the performance gains are minimal and, in fact, the 64-bit version is going to use up a bit more memory, which is why the 32-bit Opera is still the default on Windows.