Opera 10 features new “visual tabs”, located above the address bar.
It’s pretty fun, but I constantly experience problems figuring which tab is opened when looking at it, especially when few are opened.
The reason is that active tab is very light-blue-framed while inactive tabs have dark blue framing. Commonly used pattern for tabs design is the one where currently opened tab is contrast and inactive one is dimmed.
I’m not sure this is a problem for most users, but in this case designers should have stuck to the popular patterns if they wanted users to quickly adapt to their application.
P. S. Previous Opera browser version used the right colouring for active and inactive tabs. :)