Interesting topic..
Nothing to hate as a tourists except rare discrimination against Chinese, probably due to the flood of China tourists spoiling the market.
But if I were to stay there, I would hate the cost of transportation and variety of food.
Their fast pace of living is scary, almost every part of the Tokyo feels like CBD area during peak hours. Can't imagine how stressful it is to live there.
Perhaps I got used to our own pace of living, when go Europe countries, their pace is super duper slow, yet they still have fairly good economy and sustainable businesses, quite amazing. It just puzzles me why most ppl from countries in asia work more than 8 hours a day but is less productive than ang mohs....