I'll throw out my two yen based on 7 years of research.

- their favourite topic of conversation is food
well... when that's all that's on TV, can you blame them?

- when travelling abroad, they care little about the local culture except food
I'd completely disagree here. When my wife and I go anywhere, even a city where we have friends live, she will spend almost no time with them, and about 90% of her time doing touristy crap... almost none of it food. Also after living in Hawaii, I see hundreds of Japanese monthly getting their pictures taken in front of the statue of the old King, which is miles from Waikiki mind you.

- when they do not talk about food, they talk about money or sex
This one is news to me. I think the fact that most Japanese are part of the seniority based system, there's not much mystery as to who makes what, thus not as taboo to talk about. About the sex thing... if you're talking about men... well.. .what do you think American men talk about?

- The proverbs "money doesn't buy happiness/love" or "don't judge a book by its cover" have no significance in Japan
I hate to admit it, but I think the money one is kind of misleading. It doesn't buy happiness, but it definitely makes many aspects of life a lot easier.

- people indeed do not get treated the same way (be it in a shop, by government officials, by the police or whatever) depending on how well they dress and look.
This is very true. I was in a wreck w/o a license. The police man called his chief to ask what to do. He said, "I think he's okay. He looks like he makes money!". My jaw dropped.

- they think an opuent and expensive wedding is necessary for appearances' sake (even if that is way above their means)
Americans share this obsession I'm afraid.

- however Japanese language is so deficient in vocabulary and acurate expressions that it has to borrow thousands of new words from other languages every year
How do you think English came about? Japanese are just late to the game.

- the structure of Japanese language is so inflexible and clumsy (no relative sentences, few tenses, few nuances) that Japanese people end up speaking with isolated words (often adjectives, see below) rather than making full sentences.
You should be thankful for this one though --- means it's easier to learn, yeah?

- they can't debate and dislike serious intellectual discussions (probably due to the language issues mentioned above)
Believe me, they can -- they just don't... at least not when you're around. I used to share these thoughts, but eventually learned I was wrong. Their langauge is FULLY capable of conveying such meanings... most foreigners learning it, however, are not.

- there are very few intellectual programmes on TV (documentaries, debates, political analysis, social phenomenons, literary discussions...), due to a general lack of interest of the population
Again... is this unique to Japan? No way! In fact, America is 1000x worse! When I left the states for Japan, the X-Files & Seinfeld were at the top of the ratings. Both fiction, but you still at least had to think to some extent. Now it's American Idol and reality shows about fat people.

- they ask the same routine dumb questions to foreigners ("can you use chopsticks; can you eat sushi, is there 4 seasons in your country, etc.")
Do you have Japanese girlfriend? When will you get married?, etc.

- they tend of lack sexual morals and don't mind cheating "as long as their partner doesn't know"
Yeah, but in my stint, the 4 worst people I knew about this, two of whom screwed around on their wives were western (1 british, 3 American). Don't get me wrong, the Japanese guys were dogs too, but not on a regular basis.

- they have a computer but don't know much how to use even quite simple functions, due to a lack of interest for technology
Same on this side of the pond. How do you think IT get such good jobs all around the world?

- they throw away a dysfunctuning electronic equipment (e.g. computer) or machine, rather than try to repair it
My theory on this is that it would actually cost to much money getting it to the repair shop. Not everyone has a car... I never did. If I had to pay 3000-4000 yen each way to take a TV in a taxi to the repair shop... well... I'm 8000 yen into a new TV. Throw in the repair bill, maybe 28,000... for an OLD TV? I'd spend the extra 10,000 and get a new one too.

- they call an plumber, electrician or carpenter to repair things in their house, because they are not interested in DIY (Japan is a service country par excellence, due to people's lack of knowledge or interest in a wide array of things)
Guilty as charged. If you work 60+ hours a week, your time generally becomes extremely expensive. If it were between 20,000 yen or 3-4 (maybe a lot more) hours of me fumbling through a DIY book + the time it takes to buy the parts + the money it takes to buy the parts, I'd take the 20,000 yen any day, and go hang out in the park.

- manga, porn and fashion magazines account for over 90% of convenience stores' literature.
What about convenience store literature in other countries? I can't imagine a gas station with nothing but business magazines.

- there are virtually no magazines that test and rate products such as electronics,
www.kakaku.com I've never seen an English mag either though -- but why bother when you have the net?

- politicians are corrupted and inefficient beyond redemption, because they only care about themselves, and not the nation's welfare.
Uh... no comment (should be obvious).

Just a hunch, but I think the better your Japanese gets, and the longer you live there (and of course, the more Japanese people you meet) your views will start skewing a bit more to the "Japan isn't as extreme as it comes off". Happened w/ me.