I like rumble motors in my sabers, as long as installed well. My JQ Sabers LUKE ROTJ with it is amazing, and one that Obi-wan Ep4 that MH installed ages back, have had no flaws working for years. I am not necessarily dueling with those sabers.
I imagine that may be where the problems start to happen with these motors. I admit, it adds a nice feel to the saber, that a bass speaker doesn't. Also, positioning matters a lot with them.