Off topic, I was in a battle on the suspect ladder on Smogon last night and reachzero was there complaining about how Manaphy should be Uber :/
I don't feel that Manaphy is overpowered in the current metagame. On the PC server, where you're supposed to use Manaphy on your team and figure out how it functions, I've used Manaphy to limited success. It's hard for it to get a Tail Glow up and effectively sweep thanks to Pokemon like Tyranitar and Latias that can take hits from Manaphy quite well and threaten it with STAB Stone Edge, Crunch, Draco Meteor, etc.
Manaphy is most commonly seen in OU with the Tail Glow+ 3 Attacks set. Manaphy usually runs its attacks as Surf, Ice Beam, and Grass Knot(Hidden Power Electric isn't that common, usually teams built around Manaphy deal with Gyarados before Manaphy comes in). I've found through battling that Vaporeon makes an excellent check to Grass Knot Tail Glow Manaphy, especially if Vaporeon runs Toxic. Energy Ball Manaphy does give Vaporeon problems, however, but that's when something else needs to step in and take the hit (i.e. Latias).
I've also found that Blissey doesn't do so well against Manaphy as it does to other special sweepers, since a TG LO Surf can effectively 2HKO D_A's Wish Bliss set.
