I finally rode to work, 23km diagonally through the heart of Tokyo, without the option to avail myself of any riverside paths. Now that is 23km, most of it as busy as the busiest 2km through the centre of Toronto: 23km of exposure to Toronto's thickest traffic would never be worth risking (and would take some real masochism to reproduce, no offence to working messengers). In Tokyo? I had to keep my wits about me, and my hand near the brake hoods, but nobody but the taxi drivers were a real threat. What has happened to the age (upwards) and quality (downwards) of taxi drivers here since the 90s? Kazuhide is the best reference.
The lights are too damned long. It's like the lights in the suburbs of N.American cities: you can listen to an entire song on your car radio. It's an odd thing that cyclists in Tokyo ignore as many lights as they can get away with, yet pedestrians and drivers won't much, yet these are the same people, as most Japanese use all three modes in their lifestyles.
It's a good way to get to know any city, if it is safe enough to do. It is especially revelatory in Tokyo, because you don't travel through it much at street level. The most efficient way to get around is underground, or on elevated rail. The Tokyo commuting experience I liken to travelling by submarine: you pop up into a neighbourhood, and you go down again and emerge in the next location. If you do make a point of taking a look at a map, then walking or driving between areas, it is a surprisingly small city in the centre (within reach of the Yamanote-line). Get off the trains and you might find you could walk between two points faster, much less bicycle. This is heightened because Tokyo neighbourhoods turn their backs on their noisome avenues, and their faces to their stations, so you never know two 'hot-spots' may be across just one avenue.
Tokyo is veined with multi-lane roads and expressways, which chop up the city just as violently as other cities. Although these are safer to cross than in N.America, they are not any more pleasant to walk along. Each major, or minor, neighbourhood is pleasant to walk around closer to its central station, even though there may be few sidewalks and mixed foot and wheeled traffic, because cars cannot dominate. Further out the proportions are reversed, but still cars cannot bully, because the legal consequences of a collision are very dire to drivers. It's no Copenhagen (not least because they have a domestic automobile making lobby), but it is a huge improvement on 'home'.