Tokyo subway is much better than Beijing's; here you will never get a seat no matter when you travel (not just rush hour), the transfers are wicked long, the system is also not very connected. It is very cheap though, only 2 RMB (~30 cents?), which explains why it is so crowded. With a taxi, I really have to make sure not to travel when traffic is bad, and it is much more expensive (50 RMB), but I can use my computer in the cab.