The Olympus M.Zuiko 25mm f/1.8 has been replaced by the OM System M.Zuiko 25mm f/1.8 II. The new lens now boasts weather sealing and also includes a lens hood in the box, both of which are absent on the original Olympus lens. However, the optical formula and performance are the same. You can read my colleague James' full review for more information on the newer version of the lens.
Ask a full-frame photographer to choose just one prime lens and it would often be a 50mm, thanks to its entirely natural viewing perspective. Taking the 2x crop factor of Micro Four Thirds cameras into account, the Olympus M.Zuiko 25mm f/1.8 gives the same field of view. Sure, f/1.2 and f/1.4 lenses enable faster shutter speeds under low lighting conditions, and a tighter depth of field, but f/1.8 is also a favorite for keeping a reign on size, weight and expense.
