I love the Moog touches, they have this buzzwooshing sound that just kind of warms up and thaws like the ice that goes away in the face of the Sun in the lyrics.
However, I also think the Moog is the *least* crucial instrument in the song. It would still be great without it, and sometimes I don't even notice it.
It's nice to see how George was putting electronics
The Moog is used very tastefully on Abbey Road, but the acoustic guitar version of Here Comes The Sun with Badfinger from the Concert For Bangladesh, and the duet with Paul Simon on Saturday night live, and any time I play it on my Martin HD-28 all prove that it's just a real pretty tune, even without the Moog.