There are times when your on someone else's PC, and you have to edit some code, and you suddenly give out a massive sigh because all you have available is notepad. IE 9's dev tool makes me feel like that. My main issues are that you cannot right click on an element and inspect it, and it's difficult to edit styles. I personally FireBug, FireBug-lite, the Webkit inspector and Dragonfly to be much nicer to use.
But my browser usage is quite complicated. It's not uncommon for me to be using 3 browsers at once, and not always for web work. My main browser is FireFox, that's what I use for FaceBook (and what I'm using right now), and it will probably stay that way for a long time. There are little bits of UI functionality that I think FireFox does better; like how it even preserves the contents of text inputs in your history after a crash or browser restart. It's that detail that I think makes FF the best.
But I usually always have Chrome open too, and which I have run to always be in incognito. That's mainly for web work, so I never have to worry about cookies/cache/saved passwords when doing web work. I always get a clean slate, and if I think it's dirty then I just restart. FF also freezes when I wake my PC up, so if I turned it on to look something up then I'll often use Chrome instead.
I also run multiple desktop software, and my 4th desktop is my music desktop. So I also usually have IE 9 on that desktop, on my main monitor with Grooveshark open. That is because IE 9 is the only browser that works across multiple desktops without issues; FireFox and Opera just don't open whilst Chrome gives an annoying error when it opens.
I also often run Opera too; as sometimes I'll have radio/video streaming on my second monitor whilst I'm working. I don't like running those in the same process as FireFox, as when I'm working FF has a higher chance to stutter/freeze/crash and so interrupt it.
Safari is the only browser I flat don't use. I even use IETester (IE 6 through
more often then that.
