IMHO, the extra production has the following effect:
It paints a complicated musical picture, which creates a certain sound to the song. Then, you listen, and listen, and listen, and dig, and focus your ears on different parts of the song, each "track" if you will, and by that point, you are IN the song - it has filled you up, you are swimming in it, and you can hear every little part all at once, each component individually, yet still see the big picture (the song in it's finished state).
having the demo version, just makes it easier to hear all the parts of the final version.
Someone mentioned they didn't like the "heeeeeeeeeeeyyyy" part being "drowned" out. I see your point, but visualize..... Bono singing, and the music enveloping him... your ears still hear him, but you also visualize a whole aural scene of the cryyyyyyyyy as a part of something bigger.
That's my rambling anyway.... sorry. hehehe.