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One mans blessing is another mans curse. I actually prefer the Opera way of doing tabs compared to Firefox.
Love or hate the way that they do things, you've really gotta respect the fact that they have a completely full featured browser including a fairly decent mail client that (windows-wise) comes packaged at 3.7megs. And even then, with a vanilla install it does pretty much everything that IE and Firefox can do faster and better (for the most part).
Of course, I can't say it wouldn't be nice to see either A) extension functionality added similar to Firefox or B) a set of developers at Opera dedicated to making some decent extensions per the communities request.
but that's just my fan-boy equipment.