Mozilla Firefox is the default browser on my PC. It is a open source web browser and was the first to bring in tabbed browsing. While I also have Google Chrome on my PC, what appeals me more in Mozilla is its small RAM footprint(almost a third of chrome and helpful if you are using a machine with 2 GB or less RAM), and also tons of extensions and add-on that the open source community behind it creates.
Compared with its close competitors(Safari, IE, Chrome), Mozilla Firefox has the fastest load time. The single-click bookmarking is a breeze too.
The browser interface seems very intuitive to me, and provides lots of user configuration options. Couple of months ago my flash player kept on crashing and a master reset using the about:config option resolved it.
Being open source, upgrades are pushed out regularly, and this keeps the browser updated. The advantage to this being that the security loopholes are ironed out faster, making Mozilla Firefox very difficult to be hijacked by malware.
Mozilla Firefox remains by far my best browser.
Verdict: Time tested and proven! A Definite Go!