Version 4.0.10 is the first version published on the Opera add-ons site.
Opera support is in the early stages, and while it seems to work reasonably well, there might be issues I am not aware of yet. Please report any issues you find.
Also, we could still use some more translations. In particular for the Japanese language, as DownThemAll! has many many users the Firefox Add-on stats provided by mozilla indicate. But of course every translation is welcome!
Please see the translation guide in helping out.
PS: A version for Chrome should be available soon, too. It is currently pending review from Google.