After reading many posts (rational, ir- and all in between), here is my take (if I rip of your thoughts/posts, consider it an homage):
1) Gus committed to Auburn for 3 years...and that's what he gave. He probably WANTED the Vandy job last year, but didn't want to earn the rep of a liar amongst his coaching brethren.
2) After year 3 Gus interviewed for a pretty good gig in UNC. He was (speculation warning) likely passed over due to a glaring gap in his coaching resume: collegiate HC.
3) He took a gig on familiar ground, with a loaded roster, with which he can make immediate noise and garner some instant interest to be parlayed into a big-time gig. He will be the man, responsible for the entire program. I'll be very surprised if he's at ASU after 2 years.
4) Problems with Chizik/Auburn? Pfffft. He probably chafed, like any strong-willed and competent person, under authority, but realized that coordinators have to defer to the head man. If there was ill will, I doubt he'd stick around for the Chicken Bowl.
Parse away, fret, chew your fingernails and shake your fist at the ill-winds of fortune, but the end is NOT nigh for the Auburn Tigers. Chizik, when he was hired, spoke of always having a list of assistants that he would want to hire. I doubt he's ignored that list in the last three years. He put together a mostly great coaching staff the first time around (remember...not much turnover in 3 years) and I trust the guy to do it again.