Zoom has been used by our organization for more than 2 years. We use it across the whole organization as a tool for both internal and external communication. Zoom allows us to have a good quality video and audio calls with our colleagues, existing and potential clients and partners from all over the world.
I like the idea of Zoom Rooms a lot, but it is more for medium and big companies. We are a startup company with not a big team. I do not see the need to use Zoom Rooms yet. In the future, we will most likely consider Zoom Rooms.
Zoom was created by the same team that created GoToMeetings, but GoToMeeting now belongs to Cisco and prices are very high. Zoom has the same features and even better quality than GoToMeetings, but prices are much more affordable. RingCentral Meetings doesn't have such good quality, but costs more. Google Hangouts looks and feels like it is more for friends and family than for professional communication.
I think Zoom is well suited in any scenario when you need a tool to have internet calls with anyone be it a member of your family or your professional contact. Regarding the size of organization, I think Zoom is well suited for any size of organizations: small companies, medium companies, as well as enterprises.