I like how it allows me to book my site before checking out of another location so if there are any delays with checkout or payment problems, they don't affect where i am staying this weekend! It's also great because you can see what sites have been reserved already which helps ensure we get good spots together since many people want our same ones (which makes sense).
You still need an internet connection while using their app/website but otherwise its very user friendly once downloaded - as long has wifi works at campsite etc.. We're able too reserve multiple locations simultaneously through one account instead of having several accounts per state.