I also just switched from 12 to 20 and am very disappointed, too! There are too many customisation possibilities missing.

Immediately after starting my first session I realized two great functionalities just disappeared. And I hardly think they are extremely hard to implement again.

First, I may be blind, but the very useful bin on the right upper corner is missing. Second, Opera 12 was able to block 100% of any pop-ups. Now I have to deal with pop-up ads again, even when the pop-up blocker is switched on! I could go on criticising for hours...

I have to agree to another thread OLD IS GOLD in that case. All of the functionalities from 12 should be implemented in 20. With this version 20 you can just switch to Firefox or Chrome and be done with it...