While I can't profess to being glad that a bunch of innocents got killed, and I look with not a little contempt at the use of this event as a political football (even though I'm about to do so myself, in a way), there was a direct upside to the Challenger Disaster. NASA had subcontracted the construction of the fuel tanks to a company in Utah (I think) for political reasons. The broken logic that led to this design decision caused a breakdown in the rest of the system. Also, the launch was carried out in unsuitable weather conditions, because the mission had already been postponed once, and the president had been invited, so postponing the mission again would have caused them a loss of face. How ironic.

If Challenger hadn't crashed, NASA would never have re-evaluated their policies (or at least not so soon).