And of course the biggie, that you can no longer heirarchically navigate folders sitting in the dock.
My biggest problem, as you mention, is the ever-changing icon. As I mentioned a while ago in another thread, I have several folders docked, and use each of them for various media files while I work, plus the downloads folder and my documents folder.
As I work, download required files, shift stuff between my media folder and documents folder, the icons are not only changing each time but often end up as the same thing (ie, a Quicktime movie icon, an AC3 audio file icon). Within a few minutes I'm totally lost.
Absolutely ridiculous.