This card looks really good, but it can really be a double-edged sword. If it is played early enough in the game (say, turn 3 with Urzatron and a Plague Myr) and your life total is still near-normal, this card can really save you for a couple turns since your opponents will have to take a spell or two (depending on how you've protected it) to deal with it before they can deal with you. However, if you're at, say 2 life, playing this will prevent you from recovering any life and will leave you vulnerable to any damaging destruction (like a Detonate).
However, this card does let you play with some other double-edged swords. Cards like Manabarbs, Sulfuric Vortex, and Dark Confidant become easily-playable with this card out since there is no downside to playing them. Unlike Platinum Angel, you won't immediately lose the game if this card gets destroyed since your life total doesn't change at all, rather than dropping below 0 with the angel.
The downfalls to this card are that you can't recover while it's out (like I already mentioned) and it's an artifact creature, so it's much more vulnerable to destruction than a regular creature or artifact. Also, it doesn't prevent poison counter death, mill death, or any alternate death that Platinum Angel or a Bazaar Trader'd Abyssal Persecutor can prevent.
Pros: Prevents your life from changing
Cons: Doesn't allow for life recovery, very vulnerable