I've been using the open-source Firefox browser since soon after its appearance in late 2003. In those days I was still labouring away with the PC albatross around my neck so Firefox was an indispensable replacement for the porous, universally decrypted defences of Internet Explorer.
Though Firefox, in recent versions, has had some issues, such as slowness and a tendency to freeze, not to mention one or two security problems, the latest update has steadied things again. There are other good browsers available free of charge, such as Opera and Safari for Mac, but there is nothing as comprehensive, nor as visually attractive as Firefox. Anyone who persists with Internet Explorer, particularly PC users, is asking for trouble. 83% of computer users still do.
The plug-ins are the big bonus on Firefox, particularly its search options that integrate various search engines (and reference sites such as Wikipedia and IMDB) in the toolbar, and another favourite is the control bar for iTunes. Possibly the greatest and simplest innovation is now available as a plug-in, something that surprisingly took so long to be thought of. It is called Stumble-Upon, a plug-in with its own toolbar, which allows you to summon random web pages, according to criteria you enter when you configure your account. All it does is introduce you to page after page of sometimes obscure, sometimes famous, sometimes amazing, sometimes dull stuff. And it gives you the option too of rating the pages, thereby banishing them forever if they are not to your liking. It's great fun, and of course, a terrible distraction. You'll never work again. As for cache history, cookies and other things, there is a concern there but I assume that the good Open Source people at MozillaDev are not doing anything remiss with one's information.