I wouldn't say CM is superior to Tail Glow, though. +3 SpA is still +3 SpA, and the power output is just huge. If we were playing 4th gen Ubers, I would definitely say that CM > TG, but now that Tail Glow got the buff, it really is a force to be reckoned with. It depends on what kind of team you have though. If you have stuff like Toxic Spikes support and the like, CM Manaphy rapes face. If you're just using a plain team, Tail Glow would normally be better in most situations.
Anyway, I'm not going to stop harping on about Specs Kingdra until people start abusing it. 475 SpA with 538 Speed, STAB Dragon double-STAB Water attacks is just crazy. Even Nattorei is taking 35.80% - 42.05% from Specs Hydro Pump in the rain, so it is a one-time check at best (Power Whip doesn't OHKO, IIRC, so if you're lucky enough to hit three times in a row with Hydro Pump, Nattorei is losing). I have had so many matches where I've just spammed Surf and stacked 2-3 kills with Kingdra. In the rain, it can check a whole lot of Pokemon too, like DD Mence, Garchomp and all that stuff. It can even 2HKO standard Tail Glow Manaphy with Dragon Pulse while non-LO +3 Ice Beam fails to OHKO (hehe).