The Opera Browser made some serious headway in keeping itself relevant when it introduced a new JavaScript engine for its upcoming revision. The latest edition of Opera 10.50 beta 2 for Windows contains no new major features, some minor feature improvements, and is mostly a bug-fixing release that incorporates around 100 changes since the first beta.

Also, in an effort to prevent attention from drifting away from the Mac version of Opera 10.50, the publisher has also announced a new release candidate for the beta. While that milestone is unusual, it's not unheard of for browser publishers to do this. Mozilla released Firefox 3.5 beta 99 last summer, just prior to moving Firefox 3.5 beta 5 up to release candidate status.

Changes to the Windows version include what appears to be modest but detectable improvements to the new Carakan JavaScript engine. In tests limited because of time constraints, I scored the new Opera beta on the SunSpider JavaScript test. Over three runs, it averaged 386.4 milliseconds, compared to the 435.6 ms for the pre-alpha on the same computer. Opera 10.50 beta 1 scored just above 400 ms, albeit on a different computer. For comparison, today's update to the development version of Google Chrome averaged 416 ms over three runs on the SunSpider test on the same computer that Opera 10.50 beta 2 was tested on.

These tests are not absolutes, and even running the same test on the same browser will score differently depending on whether the browser is "warm" and in use or "cold" and freshly booted, but they do provide a snapshot that the new Opera engine is extremely competitive.

Other changes to Opera 10.50 beta 2 include a visual tweak for Windows XP users, moving the tabs on top for when the default Windows XP theme is used. Windows XP users who use "classic" mode won't see the change. An Opera Widgets panel has been added to the Opera user interface, and the RSS news reader and e-mail client have also received tweaks. The full changelog is available here.

While there are still minor bugs in ancillary features that prevent it from being a stable release, the core browsing features feel well-integrated and smooth.

The Mac release includes multiple bug-fixes from the previous pre-alpha version, including improvements to Carakan, typing speed tweaks, fixing the context menu in the Speed Dial feature, and crash fixes. The full changelog can be read here.