In my experience, one of the most difficult things about running a Star Trek game was getting the players to treat it like a Star Trek game. i.e. Just acting like their characters were Starfleet officers rather than doing some of the things PCs are famous for doing. One thing every Trek game I've played lacked is the violence treadmill. D&D revolves around a never ending cycle of fighting, killing, looting in order to become more powerful so your character can continue fighting, killing, and looting stronger foes in a cycle that ends when the campaign is over or the character is dead. The violence treadmill just doesn't work very well for Trek.But, Trek still hasn't taken off as a major RPG player.
Maybe the violence and rewards treadmill is one of the things that makes D&D so successful?