Consistent, unceasing honesty for its own sake is pretty childlike, I'd say. Considering it morally objectionable or any number of other well-founded reasons is another matter, but it is not intrinsically a good thing.
When we grow up, it's pretty normal to be forthright about your opinion (except where it's uncomfortable.) We are adamant in one belief or another and tell other people what we truly believe when they ask. Naturally that leads to a lot of petty grade-school squabbles. It becomes conditioned into you, over time, to learn to lie in order to minimize conflict. One could consider that a maturing effect.
Think about how much throw-away talk you participate in each day, and how often you incidentally lie during those brief encounters with acquaintances. If you were honest every time someone picked up a smalltalk conversation with you, you could find yourself in hot water pretty fast, especially in the workplace.
At the same time, lying constantly is perhaps worse than being honest constantly if it's done without basis. Compulsive lying, for example, is a big problem with some people, and can be a sign of mental instability.
Personally, I enjoy both in moderation. I prefer to be honest, but I will occasionally lie in the sense that I evade questions and answer them only in part, out of context, or in an obfuscating fashion. I use vague statements (which could be considered dishonest) because telling a complete lie is usually difficult for me if I don't have it in mind beforehand.