If I may, I don't think Bono CAN"T sing it right for the last few years, he's simply singing it DIFFERANT. The changes in the song started on Zoo TV, and the song has changed more with each tour since. His vocals go more in that direction with the song on each tour, so even though in many of the fans opinions (mine as well) it isn't as good as the Joshua Tree/Lovetown version. I think the band were already starting to tire of this song on Zoo TV, even though they still did a tighter version then. Same goes with I Still Haven't Found What I'm Looking For, and others.
I think that given some time their joy might be reset for the album version.
The whole Bono can't sing it the same anymore just doesn't cut it for me because Bono's vox have always gone up and down during tours, and you can't possibly expect him to hit everything the same for 20 years. To be honest with you I like the version of New Year's Day on PopMart more then older versions, not because of his vocals, but the humility in his voice when he hears the crowd come in with the chorus singing with Edge, and then ordering the lights off. However on the same video I don't like the arrangement of I Will Follow for that tour. The highlights of that show for me at the Oakland stadium were Miami, Bullet, Disco, and Streets. HMTMKMKM, MoFo and Please were cool too, but I don't think it was the best night on them. The funniest thing was when everyone in the stadium drifted off on the melody to Stand By Me and Bono had to help us finish the chorus. I should also note that even though that was my first U2 I was going for the unexpected, not the hits, and swore I won't sing along to the hits.
When Pride was played early in the set, and Found, and WoWY later I noticed my mouth was making these involuntary movements and words were coming forth.