I have been an Opera user since the very beginning (and even paid a user license way back). Opera saves me time which is the best complements I can give.
My suggestion is 2 sided:
- Keep track of keyboard entries.
- Display past entries in a drop down box when new keystrokes occur and allow selection.
This will avoid the extra cut & paste keystrokes when entering the same expression on different tabs. Similar to google's prediction but based on the user's past entries. Of course add companion actions such as allow flushing of the saved entries or keeping entries after closing Opera etc.