The McCune-Reischauer system is basically friendly to Westerners. For example, Korean has phonologically no distinction between voiced and voiceless consonants, but it phonetically distinguishes them. Aspirated consonants like "p'", "b'" and "t'" are distinguished by apostrophe from unaspirated ones, which is intuitive to Westerners. The apostrophe is also used to disambiguate syllables (jon'gum vs. jong'um).
However, since it is difficult to type them, breves, the diacritic marks for vowels and consonants are often omitted, which caused serious confusion. In this case, "ŏ" (ㅓ) is simply written as "o" and "ŭ" (ㅡ) as "u". It becomes impossible to tell from "o" (ㅗ) and "u" (ㅜ). Lack of apostrophe makes it impossible to tell aspirated and unaspirated consonants.
The McCune-Reischauer system is purely based on anglophone spelling. In the beginning, most Westerners (non-english) will find it hard, to pronounce correctly.