As a huge NIN fan, I was disappointed in their cover. I actually think the whole album is generally too slow. Some musicians I expect slow from, but others I was disappointed in. I do kind of like the DM cover of So Cruel, but it doesn't really add anything to the song either.
As for using U2 covers, I'm not sure exactly how the rights go. It is still a U2 song, so I'd imagine that using the Rice version of One would still benefit U2's wallet and Mr. Rice's wallet. The question I guess would be how much the cost would be. U2 may not have even let them have their version of One.