A DPS warrior's already fairly high damage is boosted to become VERY high. This ability is also somewhat useful for soloing, since the increased kill rate will actually mean you take less damage from each mob.
At high level instances, it's sometimes wise to use this even while tanking certain encounters. While it does require that you and your healers have fairly decent equipment, boosted damage and increased rage generation due to taking more damage can greatly assist you in securing aggro during fights such as The Beast or Onyxia.
Notes
The effects of Death Wish and Enrage do not stack.
Patch changes
Patch 2.0.1 (2006-12-05): Changed this to no longer stack with Enrage.
Template:Patch 2.2
Patch 2.3.0 (2007-11-13): moved this talent from Fury to Arms. (It has since been moved back to Fury).