I love (HK) PT

A train on the East Rail line at Fo Tan(火炭)

I've been waiting for the perfect pictures for this, but I'll just have to add them later. I've been reading for years about sustainability and transport issues. If you want to read one book on the issue, read this one by Peter Newman and Jeff Kenworthy. It contains so much information in it, it needs multiple reads to absorb it all, but by the end of that, you'll never quite view transport in the same way (or at least I didn't).
They make a compelling argument, that beyond a certain size all cities need good public transportation, because this is the only way to move sufficient quantities of people efficiently, and more importantly, at a lower cost to the planetary biosphere. The car lobby (and this job is often done by governments; witness the recent bail-out of the auto industry in the US) has done a good job of disguising the fact that cars are only effective for some sorts of journeys. Trying to have an automobile based city like Los Angeles is doomed to failure, because at some point, as L.A. has now discovered, the cost of building extra freeways becomes uneconomic, however desperately you massage the figures. I believe the city of Los Angeles has stopped building freeways (or so it suggests in this old article from the New York times, and is very belatedly investing in mass transit.
Which brings me back to Hong Kong, a city where public transport works like a dream. I live a long way out from Hong Kong island, way up in the New Territories, and by the logic of most cities (or at least my beloved Melbourne) this ought to mean that public transport would be rare, or non-existent. Instead we have the East Rail line (now run by the MTR) to whisk us into the centre of it all, and what seems like countless buses to go anywhere you might imagine.

Non-peak time on an outer metro line! Note wait time!

In fact, the logic of Hong Kong transit provision seems to be that if people need to get somewhere, then there should be some form of transport that takes you there. So there are buses to all neighbourhoods, even quite minor ones, buses to tourist attractions, nature walks, markets, stations, you name it, and of course the airport, just in case you don't want to catch the fast but slightly more pricey train. Not only that, but there are all types of buses, from official double-decker routes, to the more anarchic minibus system, to the privately-funded shuttle buses of some bigger institutions. So, for example, when we headed on the weekend before last up to the scenic Bride's Pool waterfall, there was a bus (that runs specifically on Sundays and Public Holidays) to take us there, and very efficient it was too, even if we missed a couple of them, by being caught between stops. Not only do the buses run everywhere, but they run frequently. In fact a 'bad' service is every twenty minutes, but usually they run more often. Where I was living in Melbourne, there was one bus, which ran every 45 minutes during the week, and every 75 minutes on weekends. Now that's one bus you don't want to miss.
Meanwhile the MTR (地鐵站 - the subway) runs often on two minute frequencies, blowing out to a horrifying ten minutes or so on the less popular lines. I don't want to belabour this point too much, but frequency really does matter for public transportation. Some places I need to get to require four interchanges - in most systems this would be a disaster, because the services would not always connect, and it would take forever. I have done that and similar journeys at least a dozen times in my short time living here, and my journey time varies only by about five minutes or so either way, because the trains and buses come so regularly.
On a brief tourist note, don't come to Hong Kong, and NOT travel on the trams down in Central. They seem like living history to me, despite being plastered with modern advertisements. They are gorgeous inside and out, and look like giant cereal boxes, patiently lumbering their way along the road. You may not get there as fast as the MTR, but you will do it in style, and all for only HK$2 (二元).
If you tire of all the the myriad public transport options, or simply have too much to carry, then there is always a taxi around, which are plentiful, and inexpensive. Though you do have to communicate where you are going, and for that you may need a card with your destination address written in Cantonese. The lesson is, be prepared (or perhaps indicate your destination on a map on your smart-phone).
No discussion of public transport in Hong Kong could ever be complete without a discussion of the beloved Octopus card. I have used an Oyster card in London, and quite enjoyed that, but I couldn't help noticing that I seemed to be haemorrhaging money when I used it. With the Octopus card you have all the convenience of never having to buy a ticket, and fabulous prices as well. Not content to make your travelling life easier in this way, the Octopus card is starting to be accepted in more and more shops and cafes as well, so you can buy yourself a snack with your card, or perhaps get a coffee (咖啡), as I love to do. The side-benefit to this, for the non-Cantonese speakers visiting Hong Kong, is that many transitions that can otherwise be a bit of a headache in other countries, can be done with the Octopus card with no conversation at all. You walk up to the counter, put your purchase there, and then hold up your Octopus card (insert polite chit-chat here, if you want to give it a go, for example, 最近點呀), at which point the amount flashes up in Arabic numerals, so you actually know how much it costs, you put the card on the reader, it beeps, and you're away. I feel like I'm living the future, even if it is a future low on civility and human interaction!!
I could say so much more on this, but I will restrain my enthusiasm. If you have any questions about it though, post a comment, and I will be happy to answer it to the best of my still-limited knowledge.