Opera weaknesses

Finally i spotted some weaknesses of Opera browser which being unable to handle java script efficiently such as creating posts in Blogger & Friendster. On top of that, i also noticed it can't be open to new window when composing mail on GMail. Other than that, i'm pretty love of their RSS feeds & tabs handlings over Firefox.
Anyway, both of them had the pros & cons but it's enough to give Microsoft headache... :)