Oh man, do I hate RealPlayer...on a Mac it's horrible.
It takes forever to open up and forever to start playing. When it does it sounds like crap... then when you want to quit, it sits there for 30 seconds before it finally decides to give you back control of your computer.
I've had to re-install it so many times I've lost count... and every time I install it, it automatically resets all my browsers to use it, so I have to manually go back and erase them. Plus the player window is huge and takes up too much space and looks gaudy... if you want to replay anything from a specific point it has to re-buffer the entire tune again... argh!!!

Give me Quicktime. Click on an audio file and it starts playing immediately. Even if the file is 14MB you can start listening to it in seconds while it loads.
The window is tiny and easily resized... and when you quit, it actually quits straight away instead of making it look like your computer crashed.