I never had to make one tweak for Opera. Ever. Opera has almost a religious focus on coding to standards. While I bet there are specific issues with implementation, whatever happened to the concept of coding to the standard and let browsers do their work?
Do Blogger features really need HTML5 WebGL 2.0 or something? I can understand some layout issues and willing to excuse them, but to not support them functionality wise is really sad, especially when you're the biggest web property on the internet. This is a throwback to the days of "Best works in IE(TM)".
To add insult to injury, I sometimes get messages like "Need a faster browser, Get Chrome" on Gmail.