It's high risk, high gain. A gambler's spell. If you aren't a gambler then I can see how it wouldn't appeal.
I got good use out of it in our last long D&D campaign. Our city had been invaded by a MM III lizardman army. All out war, blood on the streets. My necromancer used MJ and the party half-demon flew around with the gem. I'd take over lizardmen, start fights, hop back, repeat. As a tactic it had a lot more staying power than tossing a few fireballs.
My best use was when the half-demon was grappled by a gigantic siege crab. Things looked bad for him and I was MJing trying to get the crab or the controller. By mistake I got the half-demon....
and cast dimension door from the grapple, saving his life. (He was on 1 hit point).
Also I find the body hopping to be fantastic fun.