I used a Sony DSLR for a few years and loved it. I took it in to the shop to get cleaned and looked at mirrorless. I got the Sony back after a few days and now 13 months later it's still wrapped in the bubble wrap the shop gave it to me in. In Dec '15 I picked up an Olympus OM-D E-M10 II. Lots of letters there. Anyway I'm not a pro photo guy but an avid enthusiast. For my needs the Oly fits well. It's lighter and more compact so easier to take along. It fits in a Wolfman Enduro tank bag (motorcycle) on my Suzuki DR650SE just fine. If you get their E-M5 or E-M1 bodies they are dust and water sealed as long as you're using one of their several sealed lenses. A buddy has the E-M5 and has shot in the rain before, not needing a case or plastic cover for the rig. And as far as low light or night photo's I use a tripod and have no issues with nightscapes. It isn't the best for capturing stars, etc, but that was not my thing before anyway.
When I want a point and shoot I use an Olympus Tough camera. Water/dust/shock resistant so it can take punishment. A friend of mine had the Nikon version and he took it on motorcycle rides like I do. I got the camera refurbished from Olympus and it hasn't given me any problems.
Sure they're not full frame or APS-C crop sensors, you're not going to get spectacular poster size prints with them (my mirrorless has a 40MP mode so can) but how many of us actually do that? At best I do roughly 8x10 prints, rarely. I don't have Photoshop or Lightroom on any of my computers. I use a free photo editing program called PhotoScape that, in my opinion, does a lot more than a free program should do. I mainly use it for resizing for the internet, some cropping and some touch ups or changing to black & white.
I have several friends that are into photography more than I am. They use full size Nikon and Canon rigs. One guy that uses Nikon is a pro as he gets paid to go to events and shoot, he also does location portraits. Several drag their enormous cameras around on their BMW or other motorcycles. Where there's a will, there's a way. Everyone has their preference. I choose not to use a full size camera anymore.
BTW, when I got the mirrorless I told my wife the cost would be offset by the sale of the Sony. I haven't sold the Sony yet. It's still a great camera and I have quite a nice kit with it but I don't use it anymore. I guess it's a backup.