Ok, to run down the casuality list so far...my Dwarfs have killed a 2 inch mbuna cichlid when they were 1/2 inch long (6 vs 1), chewed up 3 Albino cories (one didn't survive), shredded the fins on 4 Dwarf gouramis( all this in the first week we had them). They have also killed 1 male guppy, 1 male swordtail, and chewed up 2 female swordtails (these were the fish I cycled the tank with and they had nowhere else to go). They (I have 8 now) presently reside with 3 South American Puffers, 5 Ottos (who they ignore), 2 Bumblebee Gobies (really should be in BW) and the 2nd and 3rd generations of guppies (mostly ignored as well). I think they went after the swords and the male guppy because they were a little too aggressive at feeding time and peeved off the puffers (they will work as a pack when they are holding a grudge against another fish).
Bottom line here is no mattter what tankmate you attempt to house with puffers there is a chance there will be trouble. The more aggressive the other fish is the more chance there will be a problem.