I've said this before, but I'll say it again here. I'm not at all well-versed in Opera. I've only started it up a few times to check a site for problems. My primary "issue" with Opera was in opening it for the first time...I felt totally overwhelmed by everything that was in front of me. I am not a casual Internet or computer user. I use the Internet everyday as part of my work, and I have been on the Internet from the time when my employer had Mosiac installed as a browser--the early 90s. That is my only knock against it--the GUI is overkill. Since I started in to doing my own site, I have realised that browsers are more than, well, "browsers." I have several installed, and I regularly check my site and others in them all. However, the one that is the simplest, and most straightforward to me, is Firebird, and that is the one that I am most comfortable with, so when I design, I work with it. I have enough stuff going on with learning things like WordPress, along with PHP and MySQL, etc., without having to learn a browser as well.
I will say this--one evening I will fire up Opera, and will work on my site. The reality, however, is that whether I prefer A over B or C or D, I need them all if I really want to create something that is accessible to most. As much as I may shun IE, for example, around 80% of the world uses it exclusively, so, I better make sure that I can produce a page that won't break in the various flavours of IE.