Its true that usability or 'ease of use' leads to good user experience but just that doesn't cut it. To achieve good user experience there is still more work left.
The door knob shown here is super usable and also follows the first rule of heuristics - visibility of system status. You press a button and the door is locked. To open the door you don't even have to "unlock" it. Just turn the knob and it automatically unlocks and opens the door.Whats the problem now?
It doesn't "really" make me feel secure. It actually makes me feel stupid and thats bad.
After locking a door by whatever mechanism I usually recheck it by trying to open it again, just to be sure. I'll only be satisfied if the door refuses to open. This lock doesn't allow me to do that. If I try to recheck, the door opens. Once my dad was trying to lock his hotel room door with a similar door knob from inside and he kept on opening it again and again and started complaining that it was not working. In the end I had to give him an assurance that once the button is pushed, no one can open it from outside. He was half convinced even then.
User experience is a combination of many design aspects like info architecture, user interaction, usability and visual design. The right balance of all the them is what creates a good user experience.
