I really like this card. It's a very reusable tutor at Instant-speed that works well with its colour. Turn that Black Cat into a Boris Devilboon with a Swamp in tow! You could also use this to devastating effect with cards like False Prophet (you can get a good creature to play right after), Child of Alara, or Solemn Simulacrum for a huge card/mana advantage. I do have a couple of minor issues with this card though. First, it costs 5, so unless you're running mana ramp or some way to cheat it out (Entomb/Exhume for example), this card is going to be coming out in the late game, but that's not always a bad thing since it''ll give you a steady supply of lands and creatures. The other thing is that this only searches for Zombies, so unless you're running Conspiracy, this can only really go in a Zombie-tribal deck. Still, it's a good card for Zombie-tribal decks.
Pros: Instant-speed creature and land tutor
Cons: Requires sack, looks only for Zombies, high cost