Forward: I'm not a Lennon fan. I think McCartney is a better song writer.
The song sucks. It's typical of Lennon; it's mostly political, and people appreciated Lennon for that. But Lennon's no Bob Dylan. Dylan's protest songs are catchier, his voice fits them well, and they generally have a more positive outlook. Rolling Stone's list of the top 100 songs supports this. As a solo act, Lennon had one song, Dylan had 4, 5 if you could Hendrix's cover of "All Along the Watchtower."
And how does this apply to Darfur, again? Why a Lennon CD for Darfur? And two covers of "Imagine" on the same compilation?
As a solo act, Lennon's overrated, and the "Instant...Darfur" album is proof.