The ease of use for my end-user customer base. There really isn't anything I dislike at this time however there are only two things that I can think of - 1) being able to back up more than one domain or 2) being able to create multiple backups in case the main server goes down. If you're looking to give your customers peace of mind then you need to look no further! We've been using Backup CP since it was released and we haven't had any issues what so ever thus far. Also our support team has helped us every step along the way when needed which makes me feel much safer about backing something as important as our website.