I was completely puzzled by what you described in this thread, primarily because I don't recall ever reading a single report of this issue happening with an Aveo. And with the exception of a pulley bolt coming loose, I've never read an account of one of these keyed junctions breaking down on any other vehicle either. And from those pics that you just posted, there doesn't appear to be any sign of wear on either the key or the keyway.

My guess is that when the pulley isn't pinned in tight by the balancer bolt, there will be some very small amount of play. If the pulley can be slid off the shaft without needing to be forced off with a puller, then how can there not be some tiny amount of wiggle room? IMO it would be a huge mistake to give up on this Aveo just because of what you're finding with this pulley. I'd button it back up without a second thought if it were one of mine. JMHO, FWIW.