I'm glad they executed him. Maybe he is changed, and I'm not going to argue against personal forgiveness such as that which surviving victim Rais Bhuiyan has granted him.
But law is about more than just vengeance. It is about justice, and about setting standards for a society.
When someone kills a bunch of innocent people as retaliation for a terrorist act committed by someone else, they deserve execution.
This is as opposed to a case such as the Jerome Ersland case (which I first heard about from Lawrence Auster). While I think that Ersland's act in killing a would-be robber long after subduing him was, indeed, murder, I think that it would have been much more fair to have lowered the charges to second degree murder rather than first; even if the later shots were not justifiable, the fact that the victim was part of an armed robbery attempt should mitigate the charges somewhat.
That is all.