The Center for Responsible Nanotechnology has a nice overview of its current findings on molecular manufacturing here, which summarises the pros and cons of being able to manipulate matter in a controlled way at the molecular scale.
Molecular manufacturing is fundamentally different from the "heat and stir" approach to building things with molecules, because it aims to directly control the placement and interaction of individual molecules. This opens up lots of new possibilities for building things (beneficial or dangerous), and the world will not be the same when the transformation to molecular manufacturing has occurred.
This revolution in manufacturing will make the Industrial Revolution seem trivial in comparison, and it will happen within a small number of decades (CRN says 2 decades). This means that it is likely to have a big impact on the lives of most people alive today, which gives you an incentive to read all about it here.