I am in favour, and think using the death penalty as a reason against isn't a fair comparison.
I am against the death penalty because innocent people might be killed, and that isn't worth the trade-off.
Using that same logic saying that some people might be coerced into euthanasia doesn't work, as correctly killing bad people doesn't really have a postive aspect (beyond satiating revenge/bloodlust in a few).
Ending the horrible suffering of many people seems a viable trade-off for the few that might be coerced, the balance of the scales and all that (imo).
Basically, the pros outweigh cons wrt euthanasia, whereas they do not wrt the death penalty.