It's not exactly very complicated to uninstall an app in Mac OS X. When you drag it to the Trash it really is gone, so it's uninstalled. The problem is that most apps also have preferences and other auxiliary files; they are nt deleted when you remove the app.
However, there are quite a few apps that remove the files left over. One such app is AppTrap. It does it's job just as well and is free. When you move an app to the Trash, it asks you if you also want to move all it's preferences and customizations as well. Simple and effective :). Here's what it says on the Apptrap site:
The feature Apple forgot
OK, here's a fairly simple idea: what
if applications could be uninstalled
as easily as they are installed, in
other words, by drag-and-drop.
The exact opposite would have to be...
dragging the application to the trash.
Ah, there you go! This is exactly what
AppTrap does. Whenever you drag an
application to the trash, a dialog
window will pop up, asking if you want
to delete the associated system files
too. Simple as that.
So you see, using something like Apptrap really does make it seem easy. It's just a few extra files deleted along with the app.
Just as a quick note: AppTrap is no longer developed; however, it works perfectly in Leopard and the project has forked with the original authors blessing.