About the CSS bug, yeah, I see those too and VERY annoying. :/
Your SL argument might be true... but there is another side to this coin. I'll give you a real life example : I'm just one person, one tiny little dev sitting and complaining about SL and Opera. However, I am in a decision making position where I work. Which means, if I make something Silverlight ( which I actually really would like to do ) it will be pushed out to... now listen to this : 8-10000 business customers !!! each having their own websites which each reaches many end users.
Now, I want to hear anyone at Microsoft business decision section or the Silverlight team still telling me "You are just one person, you don't matter."
My point is, it's not the browser marketshare which makes or will make Silverlight important and help its adoption, it's the developers. and trust me, there are many many many like me.
Besides, Opera has almost half of Safari's marketshare ( http://marketshare.hitslink.com/report.aspx?qprid=0 ) it's still a big chunk. It's not like Linux having less than 1%. I know I sound selfish and you could say "So use IE", but the thing is that I won't. I simply won't. I use Microsoft products all day everyday both in business and private and I LOVE Silverlight and its potential. But Silverlight/Opera issue is still a big enough problem for me.