I switched from the Canon EOS System (which I used for almost 20 years, 10 years digital) to a Panasonic Lumix G5 just a month ago. I used my camera less and less because I was tired of lugging around 15 kg and more just to make some nice pictures. I used my point-and-shoot more and more, but it was limiting when taking pictures of wildlife. I thought about switching to a mirrorless camera more and more, and after some of the photographers in my nature photography club switched and were satisfied with the quality I decided it was time for me, too. I was lucky to sell my complete EOS system to another person, and with the money I was able to buy the camera, different lenses to cover the range I was used to and a new pair of binoculars.
So far I am really satisfied. I still have some minor problems operating the camera, but I guess that is normal after 20 years with another concept. The quality of the pictures is with some lenses better than with my old camera, and everything is good enough for me. My camera bag now weights about 3 kg and it is a joy to carry the stuff around and use it.
I like that I can use Panasonic and Olympus lenses (and more from third party manufacturers are coming).
(And I love the new binoculars, too! So much better than my old ones!)