Version 12 of Opera just entered beta, and you can download a copy to try out today. The release, codenamed 'Wahoo', adds a simplified theme manager, speed and plug-in improvements, and 64-bit versions for both Windows and Mac.
A handful of older features, such as the Opera Unite media server and Opera Widgets, have also been retired in this release. (Extensions are now the recommended alternatives to widgets.)
Moving plug-ins into their own separate process is a sensible move we've already seen in rivals such as Chrome. Browsers often crash because of plug-ins, but this way when that happens, your entire browser doesn't die.
We've recommended Opera before as a good secondary browser even if the main flow of your work is elsewhere, and that remains a solid approach. Opera 12 is a free download for Windows and Mac. Hit the link below for a fuller list of the added features.