I watched the video last night on VH1. And I must say I liked it very much. This is how covers should be made - keeping the original message and power of the song AND adding the band's own style.
In general I don't like anybody making Beatles and Lennon covers. But sometimes they are successful, I must admit. For example, I liked a lot "Eleanor Rigby" covered by Daniel Cavanagh (Anathema). It's always better for me when the covering artist comes from a completely different music genre. So Green Day made it well, IMO, I like how the drums step into the song and I like the distinctive Green-Day-sound at the end of the track.
I checked what the project "instant Karma" is about and apart from being glad that something is done for the cause, I'd like to listen to all the other Lennon covers, especially:
Aerosmith ft The Sierra Leone's Refugee All Stars "Give Peace a Chance" (I like Aerosmith)
Ben Harper "Beautiful Boy" (I don't like Ben a lot, but still...)
The Black Eyed Peas "Power To the People" (that should be interesting)
Lenny Kravitz "Cold Turkey" (great both song and singer)
Regina Spektor "Real Love" (one of my favourite singers, she's so amazing and unusual)
R.E.M. "#9 Dream" (well, they are not what they used to be, but...)
U2 "Instant Karma" (what can I say?!)
Youssou N'Dour "Jealous Guy" (I loooove the song)
I am very sceptic about these:
Avril Lavigne "Imagine"
Christina Aguilera "Mother"
Jack Johnson "Imagine"
Avril Lavigne, Imagine? Hello? WTF?
All the other artists are not so well known for me.
It can be downloaded via iTunes, I don't have this so I'll search through the Internet to listen to those songs. Must be very interesting, at least