What's the big deal? After all, if everything else in your program is correct, having an ellipsis in the About box menu command isn't going to make your program difficult to use, is it? While that is certainly a valid conclusion, the premise is questionable. If you don't know the standards, what are the chances that everything else in your program is going to be correct? Bad user interfaces are usually not bad because they have one or two glaring problems. They're bad because they have dozens of small mistakes that can contribute to or directly result in the following problems:
Helping you make sure that your program conforms to what the user expects is exactly what the standards are for. Complying with the standards allows you to create programs that the user already knows how to use. For example, if you use a standard list box in a standard way, there's no need to document how to use it. And best of all, you don't have to do any of the really hard work—all of the design work and user testing has already been done for you. When you create programs that don't conform to the standards, you're pretty much on your own.
Conforming to the standards makes your job easier, not harder.
I appreciate the fact that Designing for the User Experience is a fairly large book and can be difficult to read at times. However, it is effective as a reference and you really don't have to memorize it. Just have a copy within easy reach, know what's in it, know what you already know, know what you're less familiar with, and know when you need to refer to it. That's all!