I use several: Flock, Firefox, Safari, and Opera (in that order). Each has benefits...
- Flock - built-in Social Media integration, Extensible (e.g. add-ons, plugins - inherent, due to being based on Mozilla Firefox), and Customizable (e.g. Themes, re-arrange toolbars and buttons)
- Firefox - Extensible (e.g. add-ons, plugins) , Customizable (e.g. Themes, re-arrange toolbars and buttons)
- Safari - Fast, bookmark synchronization** with iPod Touch/iPhone's mini-Safari
- Opera - Fast, built-in bookmark synchronization**, across computers
NOTE: I use Mac OS X and Windows, and not LINUX [yet]. For mobile use, I use an iPod Touch.
* "Add-ons are installable enhancements to the Mozilla Foundation's projects" Wikipedia.org (my favorite add-ons)
** synchronized across computers and/or devices.
Ref: source


