It has been known to be a "party saver" on a few occasions. This trinket becomes more useful when soloing (so you don't have to run back when you die). In dungeons it serves as wipe protection. It usually won't help you in raids, unless you're a backup healer that tends to die a lot. On world bosses where a death means trouble for a raid (Lord Kazzak, etc), it probably won't be any use to you. However, it doesn't automatically resurrect you, instead working similar to a soulstone and giving you a "Twisting Nether" option along with "Release Spirit."
With the advent of the Arena, the Twisting Nether card has seen a surge in popularity. While the chance of proccing the effect is low, and the benefit of the proc quite random, the chance to resurrect in an arena battle can result in a victory that might otherwise have been a loss.
- Patch 1.6.0 (12-Jul-2005): Added.