-Add an option for the sidebar to only appear when hovered over
-Make the new tab button extend to the top of the screen instead of having a few pixels above it of dead space
-Allow users to change currency GX corner deals are displayed in. Euros aren't the only currency in the world and aren't used by plenty of people
-Add an option to have the entire window close when all tabs are closed
-Make it easier/more snappy when dragging a tab from one window to another

The last two points make it infuriating to use at times because without realising, you've accidentally left 4 windows of Opera open with nothing on them besides GX corner