I haven't managed to get a profitable operation going in the full town yet, but I did manage to get one up and running in the Tutorial town - ended up with 90% coverage (not too hard, since the town is fairly small).
A giant tram loop in the center of town, with bus branches running to the two suburb divisions. My big surprise was when I connected up a heli route to the airport / stadium across the river - suddenly, both pads starting filling up with dozens, then nearly a hundred people! I increased my heli's up to six - enough that they were cueing up, loading and unloading as fast as possible - and I still couldn't get the stations below 70 or so (unhappy) people!
An underground metro solved the problem - a single train can hold almost 10x as many people as a chopper, and moves just as fast. My profits soared when I put in the train - while my best tram was making about $300 a month, my metro was making $1,500 a month. I was also able to cut my heli fleet down to just 2, to keep up with the (much smaller) amount of pasengers that still used them.
To answer a question asked above - I've watched a single person leave his home, get on the bus, walk across the road, get on the tram, walk to the heliport, and then take the chopper to the stadium - your passengers will definately use multiple methods to get around. I'm not certain how far they're willing to walk, but it's certainly at least across the road.