In Korea, a command of Korean is not as useful as you would expect . Many Koreans speak English and are eager to practice it with foreigners, which makes practicing your Korean quite difficult. Reading advanced material is rather difficult but can be very fulfilling, as is watching the many excellent Korean films. Outside Korea, you can often exchange a few words in Korean in shops. In the US, you might get a generous portions of food from pleasantly surprised cooks in Korean restaurants, especially in the US.

If you decide to take up Korean, you should have a love for Korean and all things Koreans. Then the language will bring its own reward by providing a unique window into this fascinating culture. But if you want to learn it for monetary reasons, Chinese is probably a better investment.

48 millions speakers in South Korea and 22 millions in North Korea. There are large Korean communities in China, the former Soviet Union and the US where every corner deli seems to have been taken over by these honest and hard-working people.

The use of Korean for travelling is presently limited to South Korea, as North Korea is barred to tourists.

The dialects of North Korea (Joson) and South Korea (Hanguk) are still mutually intelligible but are gradually getting different, mainly in spelling.

North Korea has completely eliminated older Chinese characters from writings, but they are still very much present in South Korea (see below).

If you learn Korean, learn the standard Seoul dialect of South Korea. It is the most prestigious dialect and is easily understood among Korean speakers throughout the world.

If you are a Westerner, learning Korean, as with many Asian languages, will expand your cultural horizons, including the way you think about life, as well as how you interact socially with the native speakers of your target language.

Culture in the land of the morning calm offers traditions, poems, parables, and historical writings dating back at least a thousand years. The Korean language also offers unique concepts such as the reluctance to leave old hopes and memories behind, and some interesting Buddhist-based proverbs.

Korean cinema is excellent, with many big budget action movies with original and compelling plots. Some of my favorites include Sympathy for Mr Vengeance, 2009 Lost Memories and Joint Security Area. These movies are available on DVD with English subtitles and excellent DTS soundracks. Even if you are not contemplating learning the language, I strongly encourage you to watch them only for the high-quality break it offers from mainstream Hollywood movies.

Korean culture also offers a lively nightlife of spicy food and fun bars and discos and excellent food.

There are two levels of difficulty in learning Korean.

If you want to be able to read Korean on the Internet, send emails and have basic oral fluency, the language is much easier than Japanese or Chinese and can be rated - difficult to learn.

If, however, you want to read newspapers, books, street signs and have complete fluency - the language is probably the hardest you can find, harder than Chinese or Japanese. It deserves   - very difficult to learn.

When compared to Chinese, Korean seems at first an easy language to pronounce, as there are no tones in Korean. However, as the student progresses he discovers that there are many, many unique sounds in Korean, and that they escape our ear. You can listen and listen for hours to pairs of contrasting consonants and hardly get the difference - not speaking of reproducing it.

Korean is an agglutinative language, like Japanese or Turkish. If this is your first agglutinative language, you will need time to get used to building your phrases backwards. One benefit is that there is no case system.

Korean conjugation is very complex, with every verb having more than 600 possible different endings depending on degree of politeness, age and seniority. Most learners concentrate one one standard textbook politeness form.

Korean adjectives are also conjugated, with more than 500 possible endings.

The chinese characters used in Korean are very similar to those used in both Chinese and Japanese. Even more interesting for the polyglot, they are often pronounced in a similar way. For example, the word for "history" in Korean is "(r)yok sa," while in Japanese it is "reki shi"; "teacher" in Korean is "son saeng," while in Japanese it is "sen sei".

Korean is written with a combination of an alphabet (Hangul) and Chinese characters (Hanjas). Many students assume they can afford never to bother with the Chinese characters and only work with the alphabet, which you can learn in a day. But one must understand the limitations of this scope of study.

In South Korea, Hanjas are everywhere and especially in newspapwers. Although you can read the Internet only using Hangul, you need to know a considerable amount of Hanjas characters to read a newspaper. Exactly how many? With a 1000 hanjas, you can already read a newspaper and with 2000 you are better educated than most Koreans. Reading historical or litterary texts is another story algother.

You can reach basic written and oral fluency within 12 months of study at one hour a day. From this stage up the learning curve becomes flat and you are looking at several years of study before you master all the politeness forms and the hanjas you need to read newspapers.

If you speak German, the best program out there is Wilfied Hermann's Lehrbuch der modernen koreanischen Sprache (Helmut Buske Verlag, Hamburg, 1995)

For an introduction to only speaking Korean, I recommend the following:
Making Out in Korean, by Peter Constantine, 1995 Yenbooks (slightly racy terms included, but very fun, trendy and colloquial). 
Korean in Plain English, by Boye De Mente, Passport Books, 1988. 
Korean in a Hurry, by Samuel E.Martin, Charles E. Tuttle Company
A formal and more comprehensive guide to learn to speak, write and read, I recommend:
Mastering Korean, by B.Nam Park, with cassettes, Barron's, 1988, this is the Foreign Service Institute guide developed by the U.S.Government, and it is effective though dull (no pictures or illustrations). 
Also highly recommended are:
Colloquial Korean; A Complete Language Course, with cassettes, by A.I. Kim, 1997. 
Korean: Instant Vocabulary, Vocabulearn, Levels I and II, 1986. 
Pimsleur Language Program by Sung-Hyun Kirk Kim, 1998. Only 10 lessons are available so far, but eventually the full 30-lesson package would be most beneficial. 
If you can read Japanese, there is an excellent book with cassettes to teach vocabulary and writing for beginners: Kankokugo Kihontango purasu 2000, by Kim Dong Hahn, Goken Publishers. 
In buying a dictionary, you have to decide if you want to get one that uses one of the romanization systems listed above, which are confusing and incompatible with each other. I strongly recommend instead that you learn the script and get a good Hangul (script) dictionary, which may have pronunciation guides, but does not rely on a romanization system.