I've heard a little about Bangkok's waterways. Is this a good way to get around and explore? What are the best piers to make a stop at?
Yes, yes, and yes. If you're not in the center of the city where the train runs, you basically have to take a tuk-tuk or a taxi everywhere and it's a total nightmare.
Temple of Dawn and Wat Pho, which are two of the most incredible attractions in the city are right on the waterway. You can also get from there into other hard-to-reach parts of the city like Phahuratm Rd which is known as "Little India" and is a really interesting neighborhood.
Ultimately, I'd say, if you can take a boat, rather than a car anywhere, do it!
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Bangkok is a disaster to drive/ride around in. If at all possible, take the metro (when outside the old center of town) - although it is not terribly developed yet (i.e., it needs expansion to really get you to all the places you want to go). And the waterway is awesome. Any of the stops around the historic center area are great to get you quickly to the main sites.
In my opinion it's the best way to get around if possible - it's fast and cheap...8)