Aright, after struggling in the Super Singles Subway and trying him out holy shit Cloyster is amazing. I've been using a mixed set with a Naive nature and Surf and it kills the entire enemy team off 4 times out of 5. The only thing that really throws him for a loop is priority and random status hax. This thing finally netted me a victory over the super single's master, the Gold Trainer card, and enough BP to finally buy the last of the TMs.
If you're someone mildly interested in the Battle Subway for the TMs / trainer cards try him out! I thought Garchomp was a monster but DAMN, this little clam is awesome!