(Image of Opera 9.50 running on Linux)
While I have been a happy Firefox user for the last few years, using Opera has been more of 'the spur of the moment' event, after reading Slashdot.org's article about Opera's remarkable speed with respect to other browsers. While I wasn't not too keen on swapping browsers originally, I'm must say that I am pretty impressed by Opera's sleek user interface and it's high quality page renderings.
Although it is still a struggle for switching from what I'm used to, on the overall Opera is a pretty impressive browser, with some unusual features and capabilities that other browsers do not offer.
So for now I'm quite happy to give Opera a go, but it still remains to be seen if my preferences will stick in the long run.