Well, ONE downside:
You get more kill amounts every time you die. My ranger is the worst so far..8/9 times. X_x Sheesh. But if that isn't a big deal for you, no downside then, except for the cost of the powder/amulet/etc. etc.
"Come here!"
"What are you going to do, bleed on me?"
"I'm invincible!"
"You're a looney."
-Monty Python and the Holy Grail