Is learning Japanese really that difficult and what type of person does it?

The answer to the first question is "Yes". For most Westerners coming from one of the romance family languages Japanese is going to be more difficult languages to master than say, Eskimo. Regardless of what you've heard, regardless of what you've read and regardless of how many "Learn Japanese in your toilet time" book titles you've seen at Kinokuniya, the Japanese language is extremely hard to handle for most of the Gaijin world. Not content with a perfectly good alphabet in hiragana the Japanese have four alphabets (if you include romaji) and two systems of pronunciation, multiple interpretations, with the same kanji character. Then there is the distinct speaker - listener status that is specific to the Japanese language. These are all factors that can guarantee you'll have a harder time learning this language than perhaps even Chinese.
So given that learning Japanese is some kind of bizarre masochism what kind of a person undertakes a lifetime commitment to working around the subtitles of a language based in hidden convention and working out all those little squiggles. Without being overly stereotypical there are two distinct groups.

The first group of learners pick up the language along the way and can often found in load boisterous izakayas having a riot and speaking very bad Japanese. Surprisingly these people are actually excellent communicators. They always have a huge circle of friends and appear to have a secure happy out going nature. However they are often frowned upon by the second group for their poor Kanji ability and less than serious attitude. The second group can usually be determined by a slightly geeky appearance and mis-shaped cranium. Obesity and baldness are also a common factor. They take great pride in their Japanese Kanji ability collecting Kanji in a similar fashion to a train spotter collecting train identification numbers yet they remain ignorant of how the transport system essentially works.. Usually the study of Kanji starts during high school or undergraduate life at university as they become socially isolated. Finding recognition in Japan they sadly are still unable to express themselves normally or communicate thoughts meaningfully. These people have a small circle of friends, usually Japanese who are forced to work together with them. There is a high correlation between members of this group and having Japanese partners who are inept.
Yet the western Japanese speaker remains a select group. There are only about 2.5 million student who study Japanese in institutions: 1.5 million being Korean and Chinese, 300,000 Australians, 150,000 Americans and around 200,000 Europeans. Although these figures refer to millions of people they are extremely small in comparison to German or Spanish.

Depending on your language learning skills, on the quality of your teachers, courses, books and the amount of time you spend on learning Japanese, it could take you between 2 and 3 years to make a basic dent in the language. That is an investment of about fifteen thousand dollars and a lot of time. Obviously living and working in Japan facilitates the learning experience yet sadly for many of the second group, the geeks, as much as they wish to become Japanese they will always be outsiders. But being anal, this will not occur to them for a further decade. As for the first group, they’re to busy to worry about this fact and rarely care.
At some point the Japanese Language learner will want to sit the Japanese language Proficiency Test (JLPT) or Japanese External Trade Organization (JETRO) administered by the Japanese Government. These tests are not cheap and not for the faint of hearted. Significantly, the first group of boisterous party goers will not study until the last few days, although they may carry a text book around and talk about it dismayingly, they rarely open it. In contrast the second group is by nature extremely studious and live to tell all and sundry exactly how hard they study, and just how hard that study is. Finally both groups have a deep inner desire to integrate into Japanese society and at times this illusion may seem attainable. But the truth is no matter how long they live in Japan they will always be Gaijin, because exclusion is intrinsic to the society they love so much.

Dave