if it's to be done, it's best 'twere done properly.. or somesuch... didn't that irritating guy in Guys & Dolls storm out with a nasty note and everyone wound up laughing at him? Not going to be as much of a laughing matter if there's more than one of you leaving I suppose... but just make sure you write well enough to make them care about what they've done to you. Don't think I'd have the guts to do it, more power to you if it works.

Good Luck.