It probably depends on at which point you are 'saved'. Honestly, I think it's foolish to think it's risk free. It's a chemical that severely restricts the way oxygen is carried around the body by red blood cells. There's surely going to be a point where the major organs aren't dead but, aren't receiving enough oxygen either. That can't be good for them.
I don't know many case studies though. I think that's significant. If it was maiming but not killing lots of people- that would play into pro-lifers hands. They could (justifiably) be warning people of what could happen with evidence.
There have been members here who have failed with it and I've been fairly impressed with how many don't seem to have experienced severe complications.
That said, the truth is- I don't know. I think it's foolish to muck about with it though or think that it's 100% effective and painless. It carries risks- like all home grown methods do. That all said, it's likely the method I'd go with if I ever work up the courage.