[antiRepublicrat]

What usability problems does OSX have?

We can start with the Dock, which is pretty but not great for usability. Of course the only reason it's there is to woo Windows users used to the taskbar. Message to Apple: taking off of Windows UI features is not a good thing for your UI, although it does help with marketing. Luckily, the Dock can be replaced with something more useful.

[N3WBI3]

The dock is just as usable as the task bar of windows, there will be people that have a preferance one way or the other but neither can claim the other is more usable.

Of course the only reason it's there is to woo Windows users used to the taskbar.

Actually the menubar at the top that has existed as long as I can remember is more similar to the taskbar than the dock (in my opinion).