Typing this using Firefox, but I use Safari sometimes for sites that don't work on FF. I used to use Chrome and I have Safari, FF and Chrome installed on both Macs. On my iPod Touch I use Safari and Opera Mini and on my phone I use the stock Android (yes, Android ) browser.
OSX: Safari, primarily. Firefox, occasionally. Opera, rarely
iOS: Safari
Android: Opera, primarily. Built in browser (not sure what it is it just says, Internet), almost just as much as Opera.
Work Windows: IE8 (forced to use this and only this)
I was a hard core Safari user. Then just over a year ago I tried Chrome just for variety. Now I can't imagine using anything else.
Fast, fun & super efficient due to the many time saving extensions. I am completely satisfied. The frequent updates with the speed increases they bring make Chrome a very compelling browser.
The way it syncs bookmarks preferences and other features I choose to turn on, makes using my other Chrome equipped computers, tablets & smartphones a real joy. No matter what I use the experience is consistent.
Firefox on my mac, with safari a close second
Chrome on my pc.. when i have to break the dino out.
*shutter* Internet Explorer on my work machine.. that rocks Windows XP
Safari on my iOS's
Chrome on my Nexus 7
I've heard too many bad things regarding the privacy of Chrome (i.e. them logging all your address bar "typings", even if you don't visit the website -- almost like an address bar keylogger) and its security.
Safari is too "plain" (although nevertheless, it's still great and powerful). Because of this, I sometimes use Safari when doing important stuff that I can't bother to be distracted (i.e. programming).
What I love about Firefox is its security, privacy, and ability to be customized. I love the feature of Firefox Personas.