Yep - I love it. I often change between file properties(detailed), Image and Playing now all of which are significantly different in size. Auto resizing works really well for me.
But how much more ease of use does this really offer? Why not just size the window for the biggest thing you ever put there and leave it? The only thing you lose is space on the tree, but given the pane system, there is a LOT less need for the tree at this point. The only thing that needs to be added is for the pane system to extend to everything, including iPod and "CD volume" browsing, which it currently does not.
An auto-resize toggle on the AW might be the solution -- a button that alternates the AW between a normal pane (where you simple drag the border to your desired size and it stays) and the current "auto-size" way of working. This would allow fast access to both ways of working.
I have to say that back/forward buttons are GREATLY hampered when their screen positions jump every time you hit them. This defeats the whole point of their function, which is to have easy, "always-in-the-same-place" buttons with which to navigate. Forware/Back/Home buttons HAVE to stay in the same spot in order to allow fast, multiple button hits.
Larry