Here in Italy, practically everyone uses WhatsApp! There's no limit to the length of messages you can send. You can also use bold, italic, strikethrough and extrawide text and endless smileys. You can send photos, videos (even those that are too large to send via normal email), documents, links... You can make voice calls and video calls. And if you have unlimited wi-fi (as we do), then all this is totally free!
Personally, I use WhatsApp to stay in touch with relatives in Australia and friends in Italy, Venezuela, USA, Canada, Ghana, Spain and Slovenia. It's amazing!
On a congregation level we have two WhatsApp groups: The congregation group and each service group. The elders remind us of congregation or service group arrangements for field service, or of any changes due to weather or other circumstances. They also inform us of other congregation activies. When we have assemblies or conventions they use WhatsApp to make sure everyone has transport or accomodation. Recently, before the CO's visit, our service overseer used it to complete the appointments for field service.
Each member of the group is free to post anything of interest - experiences, photos, videos. Sometimes someone will use it to find a companion for field service. One brother visited the new World Headquarters and then shared his photos with us all. Often brothers will post photos from field service. In winter, we often share photos of how each family is snowed in!! We have a lot of fun!
I must add that our congregation is in the mountains in a sparsely populated area and we're all spread out in many little villages. The families tend to be rather isolated from each other. For example, my husband and I are the only witnesses in our village. So our use of WhatsApp actually contributes in a way to our unity.