Some acids are perceived immediately by the tongue, while others have more of a delayed effect. The product developer can work with both the combination of acids and the level of each to design a product with a very definite taste profile. There's room for some interesting development and more complex products with the use of acid combinations. Suppliers can provide detailed information on how to best incorporate these combinations. The following table indicates relative taste and pH for some of the acids commonly used in foods and beverages.
Bitterness is a taste that can be quite polarizing.
Either you like it or you don't. More effort should be given to incorporating bitterness into new products when you consider the tremendous success of beer and the fact that its predominant taste is bitter hops.