The number of houses sharing the fiber depends on the deployment, 16 or 32 being the most common (of course that is just the limit, you could have less). Latency isn't affected, fiber is f-a-s-t. My ping to the gateway at Bell Aliant is 1ms.
As for disadvantages you are sharing the bandwidth available on the fiber with other people. The control is tighter than cable though, with the amount you are allocated changing every few milliseconds. Bandwidth can also be guaranteed for phone and TV.