I'm not so sure about the first two, but as for U2, I think they're terrible, although you might be able to make that song work.

And as a personal rule, I'm against covering Floyd songs. Especially the suites like Echoes.

what's really odd is that i would have the same rule, silver, about covering pink floyd, but 'mother' and 'wish you were here' are just too fun to play. 'echoes,' if i ever did record it, would probably be much-reviled by pik floyd fans the world over, because it would be such a stripped-down version of the song. i LOVE the pink floyd version, it is expert songwriting at its finest. the ambient opening, the funk break, the piercing screams of gilmore's guitar during the freaky part, and the awesome return and ending... everything about the song is fantastic to me. but something about it's sound and chord progression really does lend itself to having another version of it where all of that is stripped away to reveal what is a really kickass chord progression and really cool lyrics.

i will probably NEVER record it, or even play it live, because there would be many boos, and it would only be six or seven minutes as opposed to the awesome epicness of the original. i'm just saying here, if i were to do some covers, this is the short list of what i would record.

if i had a nickel every time sombody suggested i do a nirvana cover, i wouldn't have to have a day job. so, it's a little minor revolution on m part that i didn't throw in a single nirvana song. i can play them all, pretty much, so it would be ridiculously easy for me to do so. call me a snob about it, whatever,,, i play "drain you" as if it were a leonard cohen song, and i would play a version of "polly" that's like a cross between the two nirvana versions. but that's all too easy. i like a challenge.

"state trooper" sounds like Korn
"with or without you" sounds like Anti-Flag

i can't do normal, faithful covers, that is to say i just wouldn't.
there are too many songs that i just love too much to dare re-making with my own spins on them.