The application interface of zippyapp was easy enough so that all my customers could download it from their smart phone devices without any hassles or problems! There's no problem with this app as far I have observed thus till now, but we do face very few issues sometimes while using our phones through other applications like Google hangouts etc.. But nothing serious at all! Very good platform which lets you connect directly (no registration)to your customer base within only 15 mins if not less