Unlike many other languages, many words in English do not have intuitive spelling, which means they are not spelled the way they sound. English learners have to memorize spellings and commit them to memory. Words like "onomatopoeic" or "maneuver" do not lend themselves to easy spelling. Having to memorize the spelling of many words is a negative when it comes to learning English because it requires extra work compared to learning some other languages.
Another negative aspect of learning English is that the spelling of a word is not necessarily an accurate indication of how it should be pronounced. The English alphabet contains 26 letters, but the sounds the letters make far exceed this number. Not all letters are pronounced, so the number of letters in a word does not necessarily duplicate the number of sounds in the word. For example, "catch" has three sounds -- fewer than the five letters that make up the word. Compare this to the word "cat," which has three sounds and three letters. One of the reasons English and Germanic languages prove to be so difficult is that they have words that contain consonant clusters. In many words, a consonant is sandwiched between other consonants, making pronunciation difficult.
There are spelling and pronunciation differences between British English, often referred to as the Queen's English, and American English. The differences are even more acute when you arrive in countries like New Zealand, Australia or South Africa, where some words are specific to the country. In South Africa, traffic lights are robots. You catch a "ride" in the United States, while in Britain you are given a "lift." In the U.S. you get stuck in an elevator but in Britain you're stuck in a lift. This is certainly a disadvantage, learning one version of English and then having to translate it into another.
According to linguists, English is one of the most difficult European languages to learn to read. It takes children only a year to become literate in other languages, while children in Britain take over double that time to get to the same level of literacy in their own English language. Part of the difficulty that arises when learning to read English is that the relationship between a sound and its letter is not fixed. Consider the letter "c" as an example. In the word "catch," the "c" is pronounced as a hard sound, while in the word "receipt," it's soft. Then, to make things even more confusing, in the word "encyclopedia," the "c" is pronounced both hard and soft. Show a word like "yacht" to a new reader of English, and there doesn't seem to be any logic in its pronunciation at all. This lack of logical patterns is a negative for English learners.