It is a cohesive piece of work; they care about appearances (compare default look of Firefox and Opera -- world of difference); it has nearly all of what I need out of a browser (only thing missing is Firebug); it allows MDI (child windows); little usability nice-ities that they introduced first (mouse gestures; active use of keyboard to browse, if you want; fit to width; page zooming (not just font size); integrated password manager; ...)

Firefox has always looked and felt like a patchwork of open source contributions and an uncohesive soup of extensions. I love open source. I write open source. I want open source to succeed. But Firefox is not there yet for me, and if the past few years are any indication, it'll be years more until it might be. It's still just second best.

Same here. Integrated mouse gestures, integrated arrow-key-based keyboard-only navigation, integrated content blocking, bookmark sync across computers. Firefox would do everything I want, with the right plugins. Opera does everything I want, out of the box.

Tabbed browsing.

Fast page rendering

Customisable search

Button to toggle images

Password manager

Mouse gestures

Easy per-site config for cookies etc

-Yes I know FF has these now or has plugins for them. But Opera had them first.

Yes, yes, all of the above plus I really like the email client, simple and clean; note taking-thats truely great when doing research; speeddial; the configurability lot of thinking gone it usability - it shows

And all of this without a single plugin that would be drawing the performance down.

I have to admit though that it does have some downsides as well. Silverlight sometimes works sometimes doesn't (it's actually the only thing that can crash Opera and Im forced to develop in it). There are some sites using activex that doesn't work and especially when using the email client (10k emails) it gets a bit slow to start and shutdown.

But overall great browser (using it since 3.60)

Mouse gestures.

The "graphics off" key. Admittedly less of an issue on broadband, but still.

Fast page loads.

Just generally spare and coherent design. IE is a behemoth and Firefox is a grab bag. It's rare for Opera to do something I don't like.

And maybe force of habit. I picked it up around Opera 4, when I did a comparison with other browsers available at the time and my priorities, and it emerged the clear and easy victor.