My biggest problem isn't standards compliance from Opera, WebKit/Safari, or even Firefox. The biggest thorn in my side has ALWAYS been Internet Explorer. IE8 looks great, and even IE7 is barely tolerable. I run a small gamer-heavy website, which usually means that they're up to date on technology. I still have 25% of all web hits come from IE6.
Also, congrats to the Opera and WebKit team for 100/100 on ACID3! :D Check out the WebKit Blog for celebration! (http://webkit.org/blog/)