After a couple of the earlier threads on this topic, I decided to use Pennzoil Synchromesh fluid instead of ATF in my Cobalt's manual transmission (same unit as in the OP's Cavalier).
After 20 miles or so, I started noticing that shifting was much smoother, especially going into first. I never thought that it was notchy before, but it's much smoother now. Maybe that's just the newer fluid, but the old only had 35K on it.
Just my 2 cents!