Unless you have an Android Wear device, then it's pretty much useless as Hangouts is the only texting app (so far that I've come across) that actually let's you send replies straight from the watch and scroll through entire conversations. Even if a notification is visible on the watch through a 3rd party texting app, the response is sent through Hangout. I don't really see a point in having two texting apps open at the same time so, for Android Wear users, Hangout is pretty much it.
At least it consumes less resources than Samsung's app, looks better, and integrates better with a Google account.