Anyone made any good use of this yet?

Throughout has been 700,000 app downloads per day supposedly.

For :-

Android
BlackBerry
Java (Any other Java phone I assume?)
Symbian
Windows Mobile

http://mobilestore.opera.com/

The Opera App Store is run by Appia, which is the new name for the company that came out of Pocket Gear's acquisition of Handango, so if you've used either of those companies for downloading apps before, you'll know what to expect.