Since I started Korean about four months ago, again and again I've come across an odd reaction when I mention that I'm working on the language. "At least it has an alphabet, right?" they say—as opposed to the enormous logogrammatic catalogs used to write Chinese and Japanese. Just as often, I hear, "At least it's not tonal like Chinese!" It always comes with the implication: At least it's not as hard as Chinese or Japanese!
At the risk of sounding defensive, I feel like those of us who study Korean at even the most elementary of levels need to start telling people: "Korean is a very hard language"—certainly no easier for a native English speaker than Chinese or Japanese, and perhaps even harder in some ways. The challenges may be different, but they are no less formidable. No one thinks that Arabic or Georgian or Cherokee are easier than Chinese just because they have alphabets. No one in her right mind thinks that Finnish is easier than Swedish simply because it's not tonal. So it's silly to think that Korean just opens up like a morning glory to the English speaker compared to Chinese or Japanese by virtue of being a non-tonal alphabetic language.
Both those traits only get you so far with Korean. Modern Korean is indeed written with an alphabet, Hangeul, that was designed specifically in order to be simple to learn and is form-fitted to the phonology of the Korean language. But Korean, like English, has so many exceptions, historical vestiges, and orthographic subtleties that you cannot simply "sound it out" and be even remotely correct. There is a lot of "just memorizing" spellings that are not at all intuitive. For example, just by hearing word for "eight," yeodeol 여덟, you could not guess that there is a silent "B" at the end of the word. The vowels ㅔ and ㅐ have evolved to sound basically the same, at least in the standard dialect. The consonants for S, J, CH, D, T, and SS all sound the same at the end of a word. Korean drops, elides, and compresses enough sounds that reading a line of Hangeul phonetically would result in the same absurdities as trying to read the English sentence "The knights acclimated to the weather" phonetically. You can't just learn the alphabet (which, admittedly, you can learn the basics of on a rainy afternoon) and dive into text, any more so than you could with Hebrew or Arabic or Cyrillic. Alphabets always hide as much sound as they reveal. There's also that fact that if you ever hope to read any Korean literature older than about 50 years—or a lot of official stuff, like business cards or one's adoption paperwork—you'll have to know a good deal of borrowed Chinese characters (called hanja in Korean) anyway.
Korean is not tonal, but its phonology is treacherous for an Anglophone (or any speaker of mainly western European literary languages). It doesn't distinguish between voiced and voiceless consonants—think of the pairs B and P, D and T—but it does make a distinction English doesn't make between aspirated and unaspirated consonants. On top of that, the consonants are also differentiated from their tensed versions. If all that linguistics jargon lost you, the point is basically that Korean requires you to perceive differences between consonants that to most English-speakers sounds like three identical versions of the letter P (and T, and J, and K, and S). Mandarin has some of these problems of consonant production and perception, but they're a little easier to overcome because the sounds come in pairs rather than trios. And Japanese, with its relatively limpid phonology and avoidance of diphthongs, doesn't even come close to posing the problems for pronunciation that Korean does for an Anglophone. My own experience with Chinese has been that people greatly overestimate the difficulty of learning to hear and produce vowel tones, which takes a couple weeks. In contrast, I still have a hard time reliably disambiguating the various Korean initial consonants. Japanese transliterates relatively neatly into English; Mandarin and Korean are nightmares in comparison—but whereas Pinyin is fairly standardized, the Korean transliteration systems are swapped out and adapted ad hoc with great frequency, making it a nightmare to figure out how to spell a word that you've only seen in transliteration, and also to represent the language's sounds accurately in a Latin alphabet. (Examples: bibimbap, or bibimbab? Japchae or chapchae? Ban Ki-Moon or Ban Gimun?)
I'd also argue that Korean morphology and syntax are significantly more complicated than Chinese, which results in a much steeper initial learning curve for expressing basic ideas in the language. Chinese is quite analytic, and while its demands on sentence structure are significant, you can learn to express basic ideas quickly with significant, if very awkward, parataxis. My Chinese is pretty terrible, but on just a year of classes, I can reliably express ideas like obligation, desire, causal relationships, suggested alternatives, facts known/unknown. It's also an SVO language, which abets an English speaker up to a point. Korean, in contrast, is highly agglutinative, and you need a significant repertoire of affixes in order to communicate some fairly basic ideas (like obligation and causal relationships). While verbs are much more lightly inflected than they are in most Indo-European and Semitic languages, they demand thorough internalization of principles of phoneme combination and harmony—rules that themselves carry laundry lists of exceptions. And because verb inflection conveys politeness, you are condemned to sound like an insolent boor unless you have mastered them. I can't speak about Japanese—which is more like Korean than Chinese in many of the respects that I've been mentioning—but if you can imagine trying to juggle the concerns of an agglutinative SOV grammar preoccupied with formality levels while also trying to deal with a menagerie of minimal pairs that your ears can barely discern, and several vowels that don't exist in your native language (ㅓ and ㅡ, I'm looking at you guys), I suspect that Korean has a critical mass of difficulties that at least matches and maybe surpasses that of Japanese for an English speaker.
Korean feels more challenging to me than even ancient Greek, which at least has the merit of a reliable alphabet and the occasional word with a cognate or descendant in English. And that's part of the reason why it's been hard to sink slow and fairly painful work into the language, while the principal reaction on the street is, "Oh, at least it's not Chinese!" Indeed, it's not. It may well be, at least at this first-year stage, a good deal harder.