Suicide is a permanent solution to a temporary problem. Even if I supported assisted suicide it would ONLY be for provable terminal conditions with a very short time to live.
I may be further out than some of the other proponents in this thread, but I don't consider suicide acceptable only for terminal cases in extreme physical pain. I agree with the sentiments expressed by Seneca the Younger millenia ago:
You may consider that the same thing happens to us: life has carried some men with the greatest rapidity to the harbour, the harbour they were bound to reach even if they tarried on the way, while others it has fretted and harassed. To such a life, as you are aware, one should not always cling. For mere living is not a good, but living well. Accordingly, the wise man will live as long as he ought, not as long as he can.
I find it entirely reasonable to end one's life when one feels he's lived as long as he ought to. And I think those folks who make that decision should be able to seek assistance without legal barriers if they so choose.