#3 is fairly spot on there, will add a few points. In general, it is even crazier than in India in terms of crowds, pollution, litter, traffic, poverty, etc, etc, and the sights really don't compare, but since there is such a tiny tourism industry there, you generally get a good reception from the people, which makes it an interesting place to travel. I remember meeting Banderban's city mayor just cos he wanted to welcome me to his town, never happened elsewhere!
There's always someone as hotels, restaurants, bus/train stations who can at least get by in english. However, rickshaw drivers, shop keepers, etc, generally speak nothing, so learning at least some numbers in Bengali will help you to no end.
Try and stick with the 'luxury' bus companies, really they're not expensive at all for getting between the major cities, and a world away from the absolute mayhem of local bus stations. Although, you'll have to takel ocal buses to get to Banderban and such places. Good luck!