Some people like it, and some people don’t, luckily,
Opera is so customizable that it lets you disable the new Visual Mouse Gesture feature.

Mouse Gestures will work as before, but you won’t be seeing anything to the big gray overlay everytime you do a gesture.

Here is how to disable it

  1. In Opera, write “opera:config” in the addressbar and press enter.
  2. Type “gesture” in the searchbox
  3. Uncheck the Show Gesture UI option
  4. Press Save and restart Opera

The Visual Mouse Gesture should now be gone!

Tip: You could also use the direct shortcut:
opera:config#UserPrefs|ShowGestureUI to get there faster, just type it in the addressbar and hit enter.

If you rather want to adjust the length you have to drag your mouse before the gesture is registered, you can take a look here for how to change this.