Firefox 12

• 
  Pros
  Fast JavaScript performance. Excellent standards support. Cool bookmark organization with Panorama. Lots of customization through extensions. Pinned sites for all-the-time access. Syncing for tabs, history, passwords and now Extensions. Graphics hardware acceleration. Cross-platform.
• Cons
  Lacks client-side tracking protection like that found in IE9. Lacks Chrome's built in Flash, PDF reader, and Instant page view. Trails Chrome in HTML5 support. No new-tab page helpers.
• Bottom Line
  Firefox remains a lean, fast, compatible, customizable browser that can hold its own against any competitor.