Yeah, Tony's is okay - but it's not really intended for boiling seafood. For most other Cajun and Creole cooking, it's a fine choice. And there's a better option than Tony's... but it's tough to find:
Only the New Orleans School of Cooking and a few independent groceries down there sell it. I mail order it now, two 21-oz. jars at a time.
One thing that I've learned about shrimp, is to boil shrimp for a few minutes in whatever brand of seasoning you use before adding the shrimp to a recipe. It plumps up the meat, and locks in the flavor so that it stands out from the other ingredients.