Agreed on Andy's voice. I thought their rendition of WYLATW was superb, and to me it sounded like it was a younger U2 performing that song during the ZooTV era. Sometimes I wonder what the later 2000 albums would have sounded like with a younger Bono at the helm.
Anyway, I think a big part of the reason as to why Bono just doesn't go all out anymore is because, frankly, he's done it too much. Voice strain/age aside, the dude's done WOWOY a few thousand times (recording takes, rehearsals, shows, etc). You're not going to have the same passion for the song the 3 thousandth time, I don't care what kind of lightshow/stage/100k+ venue you have at your disposal. And more importantly, you're not going to feel the same way about it like you did when you first wrote it, when you really felt it in your veins. People change, and you can't expect them to get fired up about those old songs anymore. It's ridiculous to think U2 can't wait to get on stage and run through another rendition of Pride again. Yay, the message about MLK will surely feel the same, yep.
Think of it this way--to the 40+/50+ year olds here--how proud and fired up are you about things you did when you were in your late teens/early 20s? How about that essay you wrote 25 years ago for your political class--still think it stands strong today if you were to read it out loud to the people who've heard it a few dozen times? I'm 30 now, and I'm very different to how I was 5 years ago. I can't imagine what I'll be like when I'm 35, but I know my thinking won't be the same as to when I was a quarter of a century old that's for sure.
I think Bono still has plenty of passion, but it's more in tune with their recent stuff I think. Look at performances of MOS during SNL or the Rose Bowl--the dude's screaming at the top of his lungs. Or the NLOTH song--he was really feeling it when they were playing that live during the beginning of the tour. Now throw in Streets or something, and he's going through the motions, changing lyrics at times and not looking as excited as before. The problem is, people have this thing called nostalgia coursing through their veins, and can't just let go of a specific memory they had when the band was all about performing "their song." They hear new stuff, it doesn't sound the same or "isn't as good," and complain. The band then winds up changing their setlist to please such fans and various stockbrokers who just want to hear the greatest hits.
It's a good reason as to why U2 won't put anything out sooner, and the reason why they dropped cool tunes like Glastonbury/EBW for the last leg of the U.S. 360 tour (I'm aware of the 20th anniversary of Achtung and the need to perform some songs from that time; I just feel like we didn't need to hear Pride/Streets again).