From what I've heard about this case, it wasn't just completely open and shut. If there's any doubt as to the level of involvement, I'd say commuting the death penalty makes sense.
I'm all for the death penalty in general, but from what little I know about this case, I don't think it applied here. His defense attorney said "He came to this country to die, and instead it's going to take him a lot longer to do it, and that's just fine with me." I think that's fine. The guy wanted nothing more than to be a martyr and instead he's going to be jailed and live a miserable life. I can't think of a worse punishment that our government is allowed to hand out.
From what his lawyer said, he's going to be mostly in solitary confinement during his prison stay.