The old phrase "Tell me what I need to know, NOT what I want to hear" is one of the most important phrases in business. It measuress the character or both the person doing the talking and the person doing the listening - when this idea is appreciated by both people it can make all the difference in the world.

The unfortunate reality is that people are typical punished for telling the truth.

You need to make sure that you're aware of this - the person that constantly smiles and tells you "YES!" often isn't looking out for your own best interest.  The grumpy but truthful person often will help you avoid disaster. 

Learn to judge people on results, and not by how 'pleasant' they are, and little problems won't be allowed to escalate into business-killing disasters.