Depends on what you need really. I personally use it as my main browser, but it has features I rely on constantly. Try it out; if you don't like it you can always go back to IE. I'll leave my opinion out of this because it's just that, my opinion. You should really decide for yourself before switching rather than basing your decision on the opinions of others. Although, if you do decide to go with Mozilla, I recommend Firebird if you're on Windows or Linux (there's a Mac version but it still has issues). It's like Mozilla but a LOT faster.
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