I have stayed at B&B places, and they can be quite nice ... usually, the folks who run these places enjoy having the company (not always, but usually). Particularly interesting at the breakfast table for conversation. Well worth the experience, but not for every trip - sometimes you just want/need the freedom to come in late at night, etc. Many are extra tiny places, so you should arrange everything well in advance.
And, yes, you usually have to be a bit more polite than you might at an impersonal hotel.

Basically, you are staying at the owner's home (in most of the smaller cases) and they will have expectations for quiet. As I understand it, a few will also have "No Alcohol on premises" policies, so call ahead and check.
Basically, none of these are real limitations if you understand/know them ahead of time and don't get carried away arguing or rejecting them with the owners.
Sometimes, you can find some very interesting places to stay at. I stayed at one place where the owners had done up every room - I think they had like 6 or 8 rooms - in a different theme from a Victorian era. Very nice touch. A nice couple too - the guy was a retired tech exec and made an excellent breakfast when I came down. I had come in late (called ahead of time) at about 11pm from a flight (the owners wife waited up for me) and I told them I would be down a bit late for breakfast too. So, I pretty much had the breakfast room to myself at about 9:30!
Z