Hapi was developed and is still being used by Walmart. Being backed by such a major company means that it will not lose support any time soon and most importantly it's being developed by professionals and that you will always get support for it.
Hapi seems to be made with large applications in mind. The sheer amount of boilerplate code it requires is simply not practical for a small web app. This also means that there are few examples of Hapi applications around for beginners to learn from.