I find physician-assisted suicide unseemly and repugnant, and I do not believe that I would ever want it for myself, or a loved one. I think there's a certain dignity in dying "naturally," and letting the body shut down--even if painfully.
However, from a legal standpoint, I do not see any Constitutional problems. In fact, our legal system is on that prizes the individual and personal freedom to the utmost extent possible. As such, what "harm" can come from euthanasia? I can only come up with typical red-herrings, straw-men, and policy outliers like "what if they start killing dementia patients to save money," or "what if a person isn't in their right mind to consent?" But those concerns are overblown, and aren't an argument against euthanasia, but an argument for its proper and effective administration and execution (pun intended).
Let 'em kill themselves if they want. It's their life and death.