I emerge Opera-static without any problem, unless the very bad look of fonts. I unmerge then Opera-static and emerge Opera with success. But I can't lauch Opera (/opt/opera/bin/opera). Message : /opt/opera/bin/opera: relocation error: /opt/opera/bin/opera: undefined symbol: _2Qt.darkCyan
The dynamically linked Opera is not supported by Gentoo right now. It is now masked. There is an updated ebuild for 6.0.2, which I'll add to the portage soon. You can try it out; if you do, please let me know whether it works for you. Sorry I can't be any more helpful at this point.
Forgot to say that the updated Opera ebuild is bug 4856.