Many of the mirrorless systems are quite decent, but most of them suffer from a drawback that I really hate: They do not have any form of built in optical viewfinder. I have played around quite a bit wit an OMD-EM1. Although I liked it quite well, the electronic viewfinder really bugged me. It is quite OK, one of the best I have tried, actually, but it cannot be compared to an optical one. The colors are a little bit off, it is just a little bit harder to recognize burned out highlights, and it seems to lag just a little bit. Not much, but just enough that photographing surfers in action was significantly harder than it would have been with a decent optical viewfinder. For snapshots and for landscape and portrait photography, none of these problems are very serious. However, they do make a mirrorless system just a little bit less ideal as an all-round camera for a serious enthusiast.