ad Hirohide: (…) The other day one of them said to me that he was told to work on his pitch in Japanese. (…)
Am I right to assume that the guy you are talking about is me or is there another one trying to get the pitch right even though he never had any idea what that was before he was told his pitch was not correct? 
Well, to be honest, I actually read about two paragraphs dealing with Japanese pitches in one of my Japanese textbooks and it was right at the beginning. I either must have overlooked that or forgotten about it when I first read the book about 3 years ago. In that book it says that your pitch accent will give away that you are a foreigner or that you come from a specific area in Japan and that you should try to listen to native speakers instead of learning the correct pitch accent by heart for every single word. In my case, I guess the pitch accent is not the only thing that tells people that Japanese is not my mother tongue. Maybe the day will come when only my face will tell 
I guess, in the future I’ll try to pay more attention to the way Japanese native speakers speak, but I don’t think I’ll get into all that scientific background of the pitch. I’m not striving to be perfect (in any language), even though it’s kind of nice to speak in a way that’s at least somewhat pleasant to the ears of a native speaker. This, however, may also include speaking with a slight accent (or supposedly incorrect pitch for that matter). Actually, one of my Chinese friends speaks fabulous German and I really mean fabulous. His German is so clear and his vocabulary so rich that it is a pleasure talking to him, every time. I still can’t believe that he managed talking like this in about 2 years only. He does have a slight accent but I would not even be able to tell you what accent it is and, honestly, I just don’t care. I look forward to every single conversation with him because of the things he has to say and the way he says them (and, yes, he would easily survive in any professional setting I can think of with his mastery of the German language).
I fear that focusing too much on grammatical correctness, right pitch, proper accent (and I doubt that in all these cases the concept of “correctness” can be as easily determined as in the case of grammar) may take away a lot of enjoyment of the learning process. This is not to say that you should simply ignore rules of grammar, pronuncation etc. No, but I try to achieve the goals I have set myself by getting a basic grasp of the theoretical framework (I mean, I’ve always studied some grammar rules, of course) and then try to build on that by imitating.
I clearly understand that there are people out there who have a much more scientific or “purist” approach to language learning and I certainly won’t question the usefulness of their approach when it comes to their own learning experience. Of course, it is great if anybody manages to speak like a native speaker and if they have found a way to achieve that goal, so much the better. As for myself, I’ve come to realize that I enjoy learning languages in a different way and I’m not unhappy with my results either (even though there is always room for improvement). Besides, despite all the things I still have to learn in Japanese and all the mistakes I’ve made (and believe me I’ve made plenty) I don’t recall a single situation where I was misunderstood because of incorrect usage of pitch. Vowel lengths, however, are a completely different matter.