1) You end up walking a lot more. Around my apartment is a subway station 4 minute walk away and a rail / subway station 12 minute walk away. There is also a bus stand. And walking is actually a positive thing, it takes longer to get to a train station then it would to get to your car, but as long as you plan ahead that's not a big deal. The only problem might be if I hurt myself and can not walk, I really have no plan B.
2) My monthly cost for gas, car insurance, maintenance... is $0. But the unlimited use month train pass that lets me go from where I live to where I work, about 40 miles is $160. Also, I don't have a subway pass, so every trip on their cost $2.
3) Schedules are really tight, if I make the 6:23am train I know I will be at work at 7:10am, traffic is no longer an issue. And over time, you naturally memorize the train schedules that you use a lot, so if I miss a train, I know when I need to be at the station to get the next train.
4) One of my coworkers pointed out that their are places in Japan that I can not visit without a car and this is a disadvantage. But then I realized I am unaware of these places because I always refer to train / rail maps when I'm trying to figure out where to go. So ignorance is bliss.
5) Without a car, moving is difficult. Even with the Ford Focus, I could buy a semi large piece of furniture and take it home. But, since many people don't have cars in Japan, most stores will deliver whatever you buy for a minimal fee. But then you have to be at home on some days between sometime (like Wednesday from 5:30 to 8:30). So far I have had four things delivered to the apartment and all four times the people have shown up within the first 10 minutes of their time range. In one case, they were 5 minutes early.
6) Carbon footprint.... My daily carbon footprint is next to zero, which is good. But I think my yearly carbon footprint is huge, because I'm constantly flying somewhere.
For Christmas, I got myself a Nikon D90, a very nice camera that can take 720p HD video. I took some random video of some of the trains I take to get around.
To view this, you probably need high speed internet, like comcast or DSL. To watch in HD, you need to click on the HD square in the video window.