As per the subject, does mediawiki do browser version checking and does it support double digit version numbers?. Opera is about to hit v10 in their user agent strings which currently breaks a few scripts on other websites currently although they have put in a tempoary stop gap (naming as v9.80) we should make sure mediawiki detects v10 properly.
More information can be found in their Dev.Opera blog posting entitled "Changes in Opera’s user agent string format".[1]
[1]. "Changes in Opera’s user agent string format" http://dev.opera.com/articles/view/opera-ua-string-changes/
-Peachey