Knowing the personality type of the person you're dealing with can make the difference between success and complete failure. The key to using this knowledge is being able to bridge to THEIR type. Don't expect others to know or understand how you prefer to be communicated with -- most won't and will simply talk to you like think and how they would prefer to be talked to.
And then wonder why you're not connecting!
All of the M-B measurents are important and powerful. But the biggest shorthand is the pairing of TJ (thinking, judging) vs. FP (feeling, perceiving). Right there you have, in my experience, the crux of 90% of all miscommunicaitons!