At first glance, Firefox 1.5 (we tested RC3) doesn't seem much different from Firefox 1.0. Everything is where it should be, with the familiar customizable button bars and a tabbed browsing interface. And in case you're considering a download, 1.5 RC3 is rock-solid. The only complications may be some non-compatible extensions-but we'll get to that later.

The most noticeable improvement in the user interface is the ability to reorder tabs via drag-and-drop. With Firefox 1.0, users had to view tabs in the order in which they were opened. Navigation is significantly faster, as Mozilla has implemented "intelligent caching" on the forward and back buttons, so the pages one is most likely to visit are preloaded-with no visible performance impact. User preferences have been redesigned to provide a cleaner tabbed interface, and features are more intuitively arranged.

But the most important Firefox tuneups are under the hood.

Full Review.