kanzlr
Hexaneur
grml, damn browser ate my reply 
ok, here we go again:
I own all three, the M8, NEX-5N with EVF and the GXR with mount module.
Usability
From a usability standpoint I'd rate them:
1. GXR
2. M8
3. NEX
why? The GXR is much faster than the M8, easier to hold, more ergonomic and the buttons can be configured to all most used functions (dedicated buttons for iso+/-, dedicated ev-comp, etc.). The M8 has, for me, an unergonomic shape, is hard to hold due to the sharp edges and has the known limitations of a rangefinder (and its benefits, of course). And it is slow to write RAW files and review them if needed.
Lastly the NEX...it is fast, and the 5N is at least somewhat configurable. But for example, the MF zoom button his hardwired to the lower softkey. hard to reach when using the EVF. The buttons in gereral are too flat. The body is also rather cramped and a bit too small to handhold. My hands hurt after half a day of shooting.
Focusing
with wides:
1. M8
2. GXR
3. NEX
with longer lenses (50, 90, 200)
1. GXR
2. NEX and M8 (for the 50)
the Rangefinder is DOF agnostic it is just as easy to correctly focus an 28 as it is with a 50. The GXR shows what has the most contrast, ie hardest edges in the frame. That works well, but not perfect. You don't know if you already reached peak contrast on the face of the person you focus on, for example. You just know that you are somewhat there, till you overshot. Still, it is much easier to see the plane of focus on the GXR in Mode2 than it is with Sonys peaking. The colored peaking is a bit harder to decode and I had much more misfocused shots with the NEX than expected, at least with the 28/2.8 wide open and the 34/1.4 stopped down a bit. With the [email protected] it was ok, and with longer lenses the NEX is almost as easy to focus than the GXR.
What really makes peaking more usable on the GXR, tough, it that it works a bit more intelligently: halfpressing the shutter gives you ALWAYS a clear, full frame view of the frame. It disables peaking and zooms out if you are zoomed in for focusing, so you can check the composition. Releasing the shutter button again, brings you back to whatever you used before. VERY convenient and it works in practise almost as well as a manual SLR (not like a rangefinder, though...). I have, for when I need critical focus, on a portrait shoot for example, used it this way:
* zoomed in
* halfpress shutter for rough composition
* release shutter, which returns to zoomed in
* focus
* halfpress shutter to spotmeter and re-check the composition
* fullpress the shutter
thats VERY fast in practise.
Other things to consider
GXR and M8 have hotshoes. Thats handy for a bounce flash, studio flashes or a GPS tracker on vacation (or the GXRs EVF).
Sonys EVF is way superior to the GXRs, but still it is a bit easier to focus with the GXR due to its focusing aids.
With the M8 you have to remove the bottom plate to change battery and SD Card.
on the Sony you can mount a campdater strap. with the GXR this is not possible, because it blocks the battery door. Thats very unfortunate.
and finally, a comparison photo:
ok, here we go again:
I own all three, the M8, NEX-5N with EVF and the GXR with mount module.
Usability
From a usability standpoint I'd rate them:
1. GXR
2. M8
3. NEX
why? The GXR is much faster than the M8, easier to hold, more ergonomic and the buttons can be configured to all most used functions (dedicated buttons for iso+/-, dedicated ev-comp, etc.). The M8 has, for me, an unergonomic shape, is hard to hold due to the sharp edges and has the known limitations of a rangefinder (and its benefits, of course). And it is slow to write RAW files and review them if needed.
Lastly the NEX...it is fast, and the 5N is at least somewhat configurable. But for example, the MF zoom button his hardwired to the lower softkey. hard to reach when using the EVF. The buttons in gereral are too flat. The body is also rather cramped and a bit too small to handhold. My hands hurt after half a day of shooting.
Focusing
with wides:
1. M8
2. GXR
3. NEX
with longer lenses (50, 90, 200)
1. GXR
2. NEX and M8 (for the 50)
the Rangefinder is DOF agnostic
it is just as easy to correctly focus an 28 as it is with a 50. The GXR shows what has the most contrast, ie hardest edges in the frame. That works well, but not perfect. You don't know if you already reached peak contrast on the face of the person you focus on, for example. You just know that you are somewhat there, till you overshot. Still, it is much easier to see the plane of focus on the GXR in Mode2 than it is with Sonys peaking. The colored peaking is a bit harder to decode and I had much more misfocused shots with the NEX than expected, at least with the 28/2.8 wide open and the 34/1.4 stopped down a bit. With the [email protected] it was ok, and with longer lenses the NEX is almost as easy to focus than the GXR.What really makes peaking more usable on the GXR, tough, it that it works a bit more intelligently: halfpressing the shutter gives you ALWAYS a clear, full frame view of the frame. It disables peaking and zooms out if you are zoomed in for focusing, so you can check the composition. Releasing the shutter button again, brings you back to whatever you used before. VERY convenient and it works in practise almost as well as a manual SLR (not like a rangefinder, though...). I have, for when I need critical focus, on a portrait shoot for example, used it this way:
* zoomed in
* halfpress shutter for rough composition
* release shutter, which returns to zoomed in
* focus
* halfpress shutter to spotmeter and re-check the composition
* fullpress the shutter
thats VERY fast in practise.
Other things to consider
GXR and M8 have hotshoes. Thats handy for a bounce flash, studio flashes or a GPS tracker on vacation (or the GXRs EVF).
Sonys EVF is way superior to the GXRs, but still it is a bit easier to focus with the GXR due to its focusing aids.
With the M8 you have to remove the bottom plate to change battery and SD Card.
on the Sony you can mount a campdater strap. with the GXR this is not possible, because it blocks the battery door. Thats very unfortunate.
and finally, a comparison photo: