Long-time Leica-R user here looking at making a switch.
What I like about my Leica-R equipment:
fabulous image quality, from both lenses and the DMR
good manual focus capability
great personal service from Leica USA's staff
what I don't like:
horrific service/repair cost and downtime
few spare parts
replacement lenses and bodies scarce and costly
most importantly, mass
Since my 63rd birthday is rapidly approaching and having a few injuries that won't heal I'm reminded of Ansel Adams' quote: "the best camera is the biggest one you're willing to carry". Quite simply, despite the image quality the R8/DMR and Leica-R lenses are no longer the best camera for me.
I want to carry my camera. To do that I need something lighter, a LOT lighter. I also want a camera with a bigger sensor than the DMR has, not APS-C smaller. I also prefer fully manual lenses with no electronics. This isn't negotiable; call it a personal quirk. What I've learned:
The R8/DMR is 1495g, the a7II is 599g.
My beloved 280mm f/4 APO-Telyt-R is 1875g; the Nikon 300mm f/4 PF is 755g but being an E lens I'd have to use a Nikon body. A Canon FD 300mm f/4 L is 1060g and may be used on the a7II.
The Nikon 55mm f/3.5 AI is 240g, the Leica 60mm Macro-Elmarit-R is 400g
You can see where I'm going with this - by perhaps sacrificing some image quality I can cut the weight in half, and since the a7II has stabilization with all lenses there will be times I can replace the tripod with a monopod, or the monopod with a shoulder stock. More weight savings, more likely I'll have it with me.
Am I missing anything? What I see in a switch to a7II is the option of using cameras and lenses that weigh much less, I have lens choices from several manufacturers, I gain stabilization with all lenses, and I have a foothold in a system that is growing instead of having reached a dead end. No AF with adapted lenses means nothing to me at this time. The biggest unknowns for me are the a7II's color quality vs. the DMR, and the a7II's manual focus capability vs. the R8.
Any other suggestions are welcome.