I fully support voluntary euthanasia for the terminally ill. Doctors are far too zealous about trying to wring just one more day of life from cancer patients, even when the suffering they're undergoing could arguably qualify as torture. Several of my relatives have stated in the past that should they ever be diagnosed with a fatal condition they'd put their remaining independent lifespan to productive use, then seek a dignified but quick death as opposed to a long and financially ruinous stay in hospital.
In my personal experience, the perception of death is the main deciding factor in the euthanasia/no euthanasia argument. Personally, I have zero fear of death itself, so I don't have any desire to cling to an agonizing existence that benefits nobody but myself. On the other hand, some people have such an inability to accept the prospect of nonexistence they go to completely irrational lengths to prolong their stay in the land of the living.
My only problems with the legalization of euthanasia is that it might become seen as a 'quick out' by those with debilitating but non-life-threatening conditions. There would need to be very strict oversight to the procedures, especially in regards to making sure that relatives didn't put undue pressure on the victim to take one course over another. It is, ultimately, a personal decision.