I am able use my phone with visa HQ app for all of their services so no need carry paper passport everywhere! You can also apply from anywhere in US which is very helpful when traveling internationally as well (I live out side country).
Sometimes there isn't any updates but they do respond quickly once notified about an issue that needs attention - just be patient while waiting until someone gets back at ya!! No cons yet though we have used many other apps/websites before this one was recommended us through friends who had great experience using them previously etc.. We were looking into doing international work permit applications since i'm not citizen either way its good option if needed especially considering how easy access via mobile device now days compared what most people would think otherwise! Easy accessibility worldwide without having physical document required = winwin situation. Also helps avoid missing flights due too late documents submitted / lost papers during transit between countries where passports arenot.