I have been using Dock-It for several months now and have had no problems whatsoever (currently using OS X 10.4.8). It never crashes and it does everything it says it will do. It's so easy to use and I absolutely love not having to open the finder as often, taking the direct route to where I want to go.

I tried several extra dock software, but Dock-It is the one I stayed with, and was glad to pay the $10. You can put anything you want in the docks -- folders, documents, applications, et al -- and you can have the docks located all around the edge of your screen in differing sizes. You can have them show all the time or be hidden until you mouse over them. Adding items is as simple as dragging and dropping. There isn't any documentation to speak of, because it's so easy to use. Everything you need to know is right in the preferences.

My one and only tiny complaint is that it would be nice to resize the dock icons with a sliding scale like the OSX dock. Instead, you have a choice of Very Small, Small Medium, Medium, and so on, and the jump from Small to Very Small is too much. Small is too big for me and Very Small is too small. Something in between would be good, but that is just nitpicking.