If you are moving from a DSLR or up from a point-and-shoot camera, there are two compact system cameras that currently stand head and shoulders above the pack. The Fuji X-T1 is an APS-C sensored triumph of traditional controls which even has a physical dial for ISO settings and drive modes. With this camera there is less menu diving than with most other cameras on the market (even with Leica, it should be noted). But are the controls accessible and do they work efficiently? Fuji is also renowned for its JPG processing and, if you work entirely in jpegs, the Fuji is an excellent choice. It certainly has the best electronic viewfinder in town.
The second camera to consider is the Olympus OM-D EM-1 which is better built, has faster autofocus and is more pleasant to handle. For some, though, the fact that the Olympus has the smaller Micro Four Thirds sensor (a quarter the size of full-frame) is off-putting. But it has to be said that the combination of lightning-fast autofocus and stellar lenses (particularly the new all-round star, the 12-40 zoom, equivalent to 24-80 in 35mm terms) probably gives the Olympus the edge. The Olympus will produce more keepers, simply because of its unrivalled autofocus speed, and that counts for a lot.
This exhaustive review by David Fleet, the Cotswold Photographer, is a must view if you are considering either of these two systems.