Since 2011 the EU Mont-Blanc project pushes the development of ARM-based compute platforms following the vision of leveraging the fast growing market of mobile technology for performing scientific computation. The process started almost 5 years ago with the development of prototypes based on Android dev-kits is now evolving beyond the research project, towards commercial computational platforms based not only on mobile SoCs, but also on server and HPC technology. In this talk we will introduce the experience gained porting system software, tools, and scientific applications to prototypes based on ARM technology within the Mont-Blanc project. By using several application examples, we will present behaviours observed on small prototypical platforms. We will describe how current limitations can represent fundamentals problems that programmers and architects will face developing and programming future HPC systems. Techniques to overcome these limitations will be also presented. The goal of the talk is to give a panoramic view of ARM based scientific computing from the Mont-Blanc perspective, supported by experience, lesson learned and test results.