I haven't given Opera a shot in years, but hey, it's free now, so why not?
I'm using it now as I write this. Back in the OS 8/9 days, the main thing Opera had over the competition was its smooth scrolling, which was leaps and bounds better than anything any other browser has EVER had. Unfortunately, it doesn't work anymore. It still disgusts me how terrible scrolling is in most programs (especially most browsers). As a programmer, I can tell you that it's really not that hard to implement good smooth scrolling. I've been doing it myself on Macs for years (yes, it takes work, but it's WORTH IT). But nobody seems to care. *sigh*
So, Opera's one big advantage is moot now.
It doesn't seem to have any image filters, which is really a deal-breaker as far as I'm concerned. Its rendering appears no better than Safari's, anyway, and it's interface, like all the cross-platform browsers, sucks. So I'm definitely not making the switch anytime soon.
And it seems like they don't even WANT people to switch, the way they set up their bookmark importing. Despite the fact that Opera support custom arrangement of bookmarks, when you import from another browser, it ALPHABETIZES everything. So, if I actually wanted to switch, first I'd need to manually re-arrange all my bookmarks. Uh, no thanks. I'll stick with what I've got.
Another thing I can't stand with the bookmark system is the way they handle sub-folders, in both the bookmarks menu and the personal toolbar. They put "Bookmark page" and "Open all folder items" at the TOP of the sub-menu. That means you need to go past them every time you want to get to your bookmarks, which will obviously be FAR more often than you'll want those two items. The Opera designers need to study Fitts' Law.
It might be a little faster that Safari or Camino, but...eh. I'm even less impressed with it now than I was the last time I used it.