The tint film itself rips off in big pieces usually.
The problem comes with the adhesive that's left behind. It took me a couple full afternoons to get that crap off. Pick up a bottle of ammonia and some razor blades and go at it. Heaven help you if you've got a fastback! Around the defroster wires here's what you can do (because you don't want to use a razor blade around the wires, like I did... oh well it's a summer car). spray the ammonia over a section. Slap some clingy plastic wrap over it. Continue on until you've got the whole window covered. It helps if it's a nice sunny day. If you've got a fastback, close the hatch to trap the heat in... don't worry, the ammonia smell goes away <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt='

'> Let it sit for a half hour or so... have a beverage, work on another window, whatever. Then come back and peel off the plastic wrap. The ammonia will have completely dissolved the tint adhesive. Wipe it all off, and then clean the window normally with a good glass cleaner.