The only issue with assisted-suicide, is at what point does the line get drawn between assisted-suicide and murder. If we do 'make it legal' I think there needs to be some clear definition in this area so that it doesn't end up
too grey (i.e. the method of assisted-suicide has to make it clear that the person wanted it; legal documents must be signed or something similar).
Also the question of "What happens if someone changes their mind at the last minute" needs to be answered or at least have some sort of legal context to it. I haven't spent a huge amount of time pondering the issue, but the opening of legal loopholes is the only thing that I could possibly see blocking this.
Well, I guess the other thing might be some sort of required counselling to prevent impulsive emo teens (or similar) from using such a thing (i.e. make sure that people are in a rational frame of mind when making the decision, not just running off to die because of a break-up).