Autosaving is definitely more convenient and easier to understand than manual saving. There are a lot of features I wish I had in Leopard. The one annoyance is that the Library folders are hidden, which angers me.
Okay, autosaving Where are all these versions saved, how many of them, for how long? Do I get a warning when the disk is full? Can I somehow clean up the space used by them? Will all versions follow the file when I move it onto a USB stick or mail it? Am I wasting disk space if I keep pressing cmd+S because I am used to it from Apple's own Xcode?
This was all pretty easy to answer for power users on 10.6 with Time Machine. There are hundreds of thousands of power users on the planet, and every time a document goes missing or a disk is full, one of them gets a phone call and has to clean up.
I don't mind if some people enjoy the new model, but it's too early to tell if it is easier to manage in the long run.