Thanks Bob & Ian - you have sold me on the train. I was toying with the idea of a car + driver simply because that would have given me the opportunity to stop and shoot some photos anytime I came across something interesting.

Unrelated question - normally I use klook.com to book stuff like airport transfers or even intercity car hires (with a driver), but klook's offering outside Bali appears to be quite meagre. Can you perhaps recommend an alternate site for Indonesia?