The major problems I have with the Leopard Dock are its inability to display custom icons for folders, and its inability to disable tiling (dynamic icon modification where content icons are superimposed on the original icon, and actual tiling when you click on it). To revert to Tiger way of doing things (far better in my opinion), use the following hack (admittedly techie).

Copy the following script to a text file (untile.sh or untile.command, for instance), make it executable (chmod -x untile.sh), make it a login item (add it to the list in your user's Login Items list on the Accounts System Preferences panel), and you are ready to go -- at your own risk, of course. If you run this script, you will disable Stacks completely. Note that you can also use this script by simply pasting each executable line in a Terminal window.

This script converts Dock preference file com.apple.dock .plist to text format so we can edit it, then changes all "directory-tile" to "directory", and finally restarts the Dock so the changes will take effect immediately. This has to be done on every re-boot as Leopard insists on regenerating Dock pref file each time the system boots.

To change folder icons from those horrible Leopard icons (which is what this hack enables, in addition to disabling tiling and superimposing), do a Get Info on the item with the icon you want to use. Select and copy its icon in the upper left corner. Paste it in the same place (Get info window) for the folder whose icon you want to change.

Caveat: Leopard will sometimes revert to default Dock icons and mode of operation apparently for no reason whatsoever. No need to reboot; just run the script again. You will also have to run it after you drag a new folder to the Dock if you want Tiger behavior for that folder take hold immediately.

[robg adds: I tested this one, and it works. However, be aware that the point of the hint is to disable Stacks -- with this script, clicking a docked folder opens its Finder window, and that's all.

Also, I had to change the if...then section of the script (with help from a Unix-using friend) to make it work. The lines from PIDS='... on down do one thing: kill the Dock process. I'm more of a brutalist, so I'd probably replace all of that with killall Dock, which is much less elegant but a lot simpler to understand (and also perhaps more dangerous if you have other Dock-named processes). If you run this and want things back to normal, you can either delete the Dock preferences file, or just edit the perl -0777... line and swap the order of directory-tile and directory, then run the script again.]