Well I, for one, would have no qualms using Disjunction in one of my games.
Why ?
Because, like someone said, it can actually add to the gaming experience.
Have you noticed that "tough" DMs who don't hesitate to kill a character on a bad roll or a mistake are much more liked than "mellow" ones who always try to find a way out for their players ?
Have you ever wondered why that is ?
Many players (myself and my players included) get their kicks out of challenging encounters, intricate politics and actual risk. The fact that they know their fate hangs on their decisions and the roll of a dice is actually enough to make them sweat. And when they do succeed, they know that it's only through luck and skill, and not the whim of their DM. Hence the sweetness of victory.
When you're playing with a nice DM who never kills players (or does it when there is absolutely no other choice since they screwed up so much), you won't enjoy your successes as much as you would have. A keen +4 rapier is worth that much more when it almost killed you in the hands of a skilled duelist.
Why am I speaking about death ? Because it's the same with disjunction. It could and should be used sometimes. Not always, because it has significant drawbacks for the BBEG. Your players won't use it because they want the loot, and your bad guys shouldn't as well - unless they're outmatched and it looks like their only chance.
But if they do use it, well, tough luck. Part of being a hero is facing this kind of challenge.