This is a strong, versatile deck with no pretensions to speed, but has few other weaknesses if the cards fall in your favor.  There is some strong Swampwalk power in this deck - use Contaminated Ground and Evil Presence to keep your Zombies swinging (or play a black deck, and bask in your advantage), and discard Filth early (to Putrid Imp, or Gladiator) to give all your undead hordes swampwalk.  Play Defilers just before a Ghastly Remains or Noxious Ghoul for maximum benefit.  Save the Nim Deathmantle for your Lords so they can reap the same rewards your Zombies do from their own powers.  Always cycle Twisted Abomination (unless you really don't need the mana) and always morph Putrid Raptor.  Plaguebearer is your friend against the fast deck.  Feel free to sideboard another against your swamp-makers for specific deck-types.