Chrome is my secondary browser, but due to some issues with it I don't see it being my primary -ever-.
Opera is by far my favorite because it caters to the system its installed on (Lower end systems are very stable with it, as are higher end systems), and it has every feature I need and tends to be much more stable in comparison for my usages.
Me? Only Firebug and Yslow, I avoid adding other plugins like the plague since it uses so much resource-wise already . But then I normally have 10-15 tabs open in my primary browser and 5-8 in the secondary.
If I bring up FF I only generally use 1-3 tabs and I close it completely as soon as I'm done with it.