I primarily use Firefox because it has an interface that works for me... Especially being able to fine-tune the engine/appearance to my liking.
If Chromium had a proper search box I would probably switch to that (don't like the question mark way).
Speedwise I'm not noticing much difference between the "leading" browsers, sure Firefox is slower with many add-ons loaded, but so would the competition be (I pretty much only use adblock which doesn't interfere too much).

Being a web-developer I always have multiple browsers available to test CSS, and found webkit based browser (Safari and Chromium) to work best for that, thanks to the wonderful Developer Tools (Inspector) that ships with it. The Firefox alternative (Firebug a.o.) just suck and interfere with page loading times way too much.

I never could get myself to even remotely like Opera or IE (especially the newer versions) though.
Mostly I just don't like the modern way of GUI development (hiding menubar by default and such), if/when mozilla decides to remove those bars altogether, I'll probably stop using it.

Quote from Jatodude

I went Chrome and I'll never go back. For me, it's the fastest and extensions are the best thing since sliced bread. This is how I read my manga: http://allmangasreader.com/
If you're still reading manga by clicking on the page and waiting for the next one to load, you have no idea what you're mis ...

dude, i installed allmangareaders 😀

oh please do click this!
The sweeter the apple, the higher the branch. The quieter the fart, the nastier the smell.
GUESS WHO??

Chrome on the laptop chrome on the desktop atomic on the mobile. I had firefox until someone recommended upgrading to chrome. It's so crisp in its interface I had never thought to go back.

If it was not a whore,I would marry firefox.

Would I lie to you?