If you want to replicate your M4-2 and 28mm CV kit, and your mode of operation (hyper focal/zone focus) I'd get the Ricoh GR. The "snap focus" feature is just what you need. I also am led to believe that the autofocus is fast on the GR, though probably not quite as fast as the latest generation of Olympus m4/3.
I've had the Panasonic 14mm f2.5, and found the lack of a way to set a "zone" focus frustrating. The focus by wire is no fun, either. There are ways to do this, but they are cumbersome. (On oly m4/3: Assign focus to a dedicated button, remove AF from the shutter button. Then: every time you power on the camera, use the dedicated focus button to focus on a "hyperfocal" distance object. Then fire away)
I liked the 14/f2.5, but found that I seldom used it, as I tend to the 20mm/f1.7 for most things. I recently sold the 28mm.
There is noticeable fringing with the 14mm/f2.5, one only needs to look at tree branches on an open sky, or the margins between a dark object and a light one. Later versions of Lightroom can remove it, and a strong UV filter can reportedly minimize, as well.
I'd recommend going to the dpreview forums and checking out the Ricoh and Micro Four Thirds forums to research both what people say about the GR and the 14/f2.5. You will see lots of comments about fringing and how to deal with it.
The GR has been "on my list" for a while, but would be more appealing for me if the native focal length was 35mm, instead of 28. There is a 35mm "crop" mode, though, so they may still get my money.
For an M4-2 28mm shooter, though, the GR sounds ideal.
