There's much to like about Opera
It's fast. Looks nice. Mouse gestures built in. Pretty nice mail client. Friendly user community. Etc, etc, etc...
But... the damn thing simply won't play ball with my employer's proxy configuration.
It's been a well known issue for years, and Firefox and Chrome manage to do it the Microsoft-approved way quite nicely, but getting Opera to work in what seems to be a fairly common corporate environment too has, apparently, never been a priority for Opera Software ASA.
If they'd fixed it, I'd most likely be running Opera as my primary browser, both at work (Windows) and at home (Linux).
But instead I've been using Firefox and, until KDE 4, Konqueror. Though Chrome is looking better and better these days.
Opera Mini has been my browser of choice on my Series 40 Nokia phone for years, but even that is no more, as my new Symbian touch phone comes with its own, perfectly serviceable, browser.
I've always liked Opera, both the browser and the company. But apart from other browser vendors nicking their good ideas, they're just not of much use to me. Sadly.