Couple of Simon and Garfunkel songs-

Punky's Dilemma, where the Maj7 is the predominant chord form.

America, in the C-CMaj7-Am progression. The Maj7 is really needed in that progression. I suppose the song could be done without it, but it would lose timing and interest.

One of my old favorites is "Ride the Wind", by the Youngbloods. Very cool progression which alternates between Maj7 and Dom7, going down a half step with each chord change. Starts, (to my ear), on Dmaj7-Db7-Cmaj7-B7 and then Eminor-G minor-DMaj7. This song is great, IMO, and would not be around if Maj7's did not exist. Try it, and then substitute a regular major. It doesn't work.

Now I haven't been around the Mudcat much lately. Haven't seen the threads Genie refers to. But I'd have to go in favor of Maj7. I can't see where there would be any controversy. You can't use a Maj7 in place of a Dominant 7th. If you try, it probably won't work. That doesn't make it a bad chord. You can't substitute minor for major chords either, yet both forms seem acceptible to most. (But there's a rumor that in the U.S., the Bush administration is targeting minor chords as unpatriotic. "I never heered JP Sousa play no sad songs". Thanks, BlueJay