Yeah, I'd advise plastic razor blades ONLY along with your favorite arsenal of adhesive removers,elbow grease and patience.
That said, I was able to speed up the process by first making sure the temperature of the glass wasn't drastically different from the ambient temperature and then just stuck my Steam Buggy in the corner of the windshield and very neatly got rid of the sticker and remaining residue.
A hair dryer might be a substitute but again, the plastic razor blades ,the cleaner and patience will get the job done.