I hear good things about Pinksy's Inferno. Probably a toss up over which is better, Pinksy or Palma. But I haven't read Pinksy. Between the two, I'll read whoever translates Purgatorio first.

Other ones I have read include Allen Mandelbaum and John Ciardi. Mandelbaum is blank verse and apparently a very accurate translation, but somewhat laborious to read. Ciardi reads easier and isn't bad, but its a half assed rhyme scheme.