I'm interested to hear how this turns out.

I've always been certain that buying extra seats would just end in frustration when someone decides to move from their middle seat to "my" open window or aisle seat, or the flight is oversold so someone decides to put another pax in the "empty" seats I paid for. I'm really eager to hear if this goes smoothly and as expected, without someone trying to take one of the seats (and going full-blown Karen when told no).