It will leave everyone with the impression that you were, and will always be, a professional. Which is sort of cool when you think about it. Sure, let everyone know that you are leaving for what you feel will be a positive advancement of your career. However, if you paint too wonderful a picture of where you are going, you could create jealousy and resentment. Also be sure not to talk about details like your great new salary, vacation package or benefits.
Nobody likes a braggart.
Go to the website Kiss My Freckled Ass Goodbye . Here you'll find letters posted by disgruntled employees saying what they wished they could have said to their bosses. You can live vicariously through their angry missives. But be careful . . . But just reading some of the nasty letters there will help you vicariously blow off some steam.