Yup. A protected one of these bad boys along with some serious healing (miracles, bonds, shards, vamps, etc.) can hurt hard.
I made a pvp deck for fun that focused on getting out a protected spine carapace, then antimattering the biggest enemy creatures and growing a quintessed momentumed destroyer for killing damage. When it works, it's a beautiful thing. Eternity thwarts deck out, and when it works it's REALLY annoying. Almost every enemy I played against rage-quit as soon as I played miracle, animattered their obsidian liquid shadowed dragon, or started growing a completely untouchable destroyer. It's a beautiful thing.
Fire shield is better against some decks, such as growth decks. Which is to say, if you play a protected fire shield turn 1, then you can kill any unupgraded growth creature (I believe any that start with hp >1 don't gain hp upon growing). Spine carapace takes many turns to take down growth creatures (3-4 turns just to overcome the growth, and then to slowly bring them down), but fire shield takes them out before they can grow at all.
Spine carapace is ridiculously overpowered on paper, but in practice I'm often able to win just in the nick of time before my creatures all die.