For an Opera user, it's still damn annoying to have to start up another browser. I tend to have Chrome running as a fallback but it does always grate me when people don't bother to fix their sites. And it's not as if Opera was that fussy.

Not as a principle, but in practice: when I go to a website and it's broken, I don't exactly have great faith in the quality of their products if it's a technical offering.

That depends. Out of all browsers, about 1% or less. Among the tech saavy (presumably your target customers), much more than that.