I wanted to weigh-in on this technology topic. First some background: I go on group birdwalks about 2x/year and belong to the local Audubon. I usually bird alone or in groups of 2 (hubby and I). I list my sightings on eBird and belong to Cornell. For 12 years, we have owned and operated a wildlife surveillance company and the local bird store owners know me by name. I have a good camera with good lenses and a good set of binoculars but I wouldn't call me a hardcore birder.
While I believe that ID apps have a time and a place, there is really no substitute for paging through a good field guide. You may find some people that get started birding by using an app and a smartphone, but if they are serious, they will almost always abandon the app and buy a book. I had iBird and I found it mainly useless for ID. If you know the name, you are good, but it needed to be separated by type and family. I still have it, but never use it. I tried Merlin in the early stages and found it to be very unreliable. I haven't tried Sleuth yet so I may find that useful.
That being said everyone has a spark bird that got them interested in birds. If the app help them get that spark - great.