Starting from version 7.20 (released on Sept. 23rd, 2003), there is now BiDi support in the Opera browser.
Hebrew support in Mac and Linux was last tested on v7.53 and is somewhat shaky (broken in web forms, email, notes, form widgest and tab titles - text is reversed (thus unreadble)).
Lets hope for a change in 7.60 (currently at preview 1 stage, Hebrew is b0rked there, aligned to the left, but in general there are some improvements).
Please test the BiDi support in all possible platforms available and report all bugs in Opera's forums as well as to the bug tracking system.
http://www.ircologija.com/opera/