It's frustrating since I just recently switched to Opera and personally find that it performs great, it feels better to me than Chrome, and overall I really like it. The biggest issue I've experienced and the biggest hurdle Opera has is the wholesale exclusion many sites partake in, usually via a if(opera){ //don't support}, rather than feature testing.
But then again, maybe they _did_ test it in Opera and saw it didn't work, but couldn't justify fixing it from a cost perspective. So, would you rather have the thing just be all broken or have a sign saying "This is broken in your browser, sorry"?
That being said, Opera is a nice browser and has gotten better and better with time. I of course encourage projects that can and should to support opera, but there are plenty of reasons not to support it and in most of those cases they're right not to do so.
The only reason to support Opera is personal good feelings toward Opera. The userbase is insignificant, Opera doesn't further any given political goal as they aren't open-source and they are several more-popular open-source browsers in the market that are tested against. So what's the point of supporting Opera other than just liking Opera and wanting it to be usable with your site? Not that there's anything wrong with that, but rarely is it a cost-efficient procedure.