I've been flying small and nano size RC helicopters for almost a year. My intention is to do aerial photo/videography commercially. The regulations uncertainty nationwide and locally is probably the biggest risk. Not to mention the restriction inconsistency from one country to another.
It's also important to be a competent pilot before flying with an expensive gear. I consider the DJI Phantom 2 Vision expensive. The Vision has lots of features that can aid you with flying. Hence, the short learning period. But, like any other electronic devices, they may stop working. Worse case, they stop working during flight. You will have a better chance to get your gear back in one piece, if you can fly confidently without any electronic assistance. Sooner or later you will crash.
Even professionals crash once in a while.