I agree. A psychic type move that only hits dark types and follows the type chart is just so amazing.
About the worst move debate, I would say the worst move is smog or ally switch.
Smog has a power of 20, so it has damage dealing potential on par with Rapid Spin. Furthermore, it has a mere 70% accuracy, on par with Focus Blast and Thunder/Blizzard/Hurricane when used in normal weather. For additional effects, it has a 40% chance of poisoning the target, but that reduces down to 28% after taking accuracy into effect. Therefore, it is outclassed by the higher power, higher accuracy, and higher effective chance of poison Sludge bomb.
Ally switch is a move that switches the user and an ally's (center ally in a triple battle) position. In a single battle, it is a lower PP Splash. In a double battle, you loose a turn (hopefully) cause both hits to be NVE. The fact that Deoxys-D, Claydol, and Mew are the only pokemon that lack paper-thin defenses and get the move makes it even worse, as all other users would probably fall to whatever attack they got (bar maybe a resisted weak special move to specially defensive Gallade, Gardevoir, and Beheeyem, all of which have horrible bulk, and all of them bar Gallade are slow). Furthermore, ExtremeSpeed, Fake Out, and a faster +1 priority move will all go before it and hit the intended target. Furthermore, that trick won't work against an opponent expecting it, and all users are weak to Ghost, with all but Gallade weak to Dark and all but Gallade, Natu, and Xatu weak to Bug, and spread moves will still hit the intended targets.