The most obvious problem with the English language skill of a person who has learned it as a second (or third...or more) language is that their pronunciation can make them difficult to understand. But a much less obvious problem, that can go un-noticed, is that such people often do not understand English spoken by native talkers. They often say that "all English speakers seem to speak too rapidly, so that even though I usually know the words I cannot keep up with their speech." In fact this means that they may not be able to actually hear some of the distinctions that are made in English. For example "lay" and "ray" sound very different to a native speaker of English, but not to native speakers of some oriental languages. The important point is that students of English can learn to hear those distinctions, and as they do, it will seem that all the English speakers are slowing down and becoming more understandable. Disclaimer: The author is employed by a company that produces software training systems for second-language learners of English.