There are a lot of "why I switched brands” articles out there. This isn't one of them. I haven't switched systems since I sold most of my Olympus E-series for a Nikon D700. Ever since then I've just been adding to the collection, so instead of switching brands in epic multi-year moves, I switch between cameras on a daily basis.
In the past six months I've used a dozen cameras from six brands to take over eight thousand photos. I don't usually mention them specifically here, since they're not the point of the exercise, but still, I wrote a list.
Nikon D800. 1046. Excellent for workshops. Chosen for its dual memory card slots, which let me only hand over the frequently reformatted SD card with a few SOoC jpegs on it to show in class, while I kept all of the raw images safe for further work later. Its 60mm macro lens is by far my favourite, which is especially handy at the ROM; I've also used the big Nikon for just about anything that's personally important.
Olympus Stylus 1s. 3559 – extensively used for continuous shooting. Carry-around camera, especially for weekend excursions in the ravines around the city. It's photographed waterbirds, salmon, and dragonflies; sports, street art and events, aquarium visits, and anything else that benefitted from a compact camera with a 300/2.8 equivalent lens. It's also what I used when I needed some quick off-camera TTL flash photos of running water.
Sigma DP2M. 300. Carry-around camera for several special outings, my main camera for Arterial project, and also used for Handrail and other projects.
Sigma DP3M. 719. Secondary camera for Arterial, extensively used for Municipal Water project, and my camera of choice for other projects that benefit from its small size and excellent daylight quality.
The Sigma cameras do technically count as two machines, even though they're really the same camera with different lenses permanently attached. Their setup is not quite identical, and they need different 10-stop ND filters, but they work as one.
Ricoh GR. 1040. General-purpose camera and wide-angle option when I’m using my Sigmas; popular in museums and aquariums, and even used for sports.
Ricoh GRDiv. 176. Occasional carry-around camera when I feel nostalgic or want an extra challenge. Also used for product photos that I can’t show yet.
My Ricoh cameras aren't used as much as they used to be. I'd hate to damage the GR through carelessness, so it tends to only come out for more dedicated photographic tasks than spontaneous moments. The GRDiv isn't in the same league, but it's such a nice camera that I can overlook its official shortcomings and make the best of it from time to time.
Nikon 1 V1. 811. Photographs to accompany three different audio projects due to its flexible lenses and silent operation. This is an ideal task for it since its image quality isn't very good, and unlike the GRDiv, it has no major redeeming values.
Nikon Coolpix A. 254. My beater carry-around camera, used for incidental photos, family gatherings, and a long-term documentary project. Also excellent for off-camera TTL flash photography.
Fujifilm XQ1. 218. Carry-around camera, two summer Fujifilm outings, product and general photography. Having WiFi makes this camera unusually useful; the Stylus 1s is another one that benefits from modern technology.
Panasonic TS3. 25. Underwater video and photos for World Listening Day project, summer pool parties.
Fujifilm GA645zi. 16. Summer Fujifilm walk in the Distillery District with colour Fujifilm film.
ZM Zeiss Ikon. 13. Black and white film for street photography and some portraits.
Switching between so many cameras actually isn’t all that difficult.
The Sigmas and Ricohs are four cameras with two interfaces, and the D800 has lots of clearly labelled buttons – even though I occasionally need to look up how to set a custom white balance. Using raw capture with auto-iso, auto-WB, and aperture priority mode effectively turns all of the digital cameras into point-and-shoots; the film cameras are even simpler than that. And before I use an uncommon camera ‘for real’ I’ll usually practice with it for a few days ahead of time. Sometimes those reacquainting outings produce more significant results than the project I was practicing for.
And of course a lot of the time I just pick up a camera because it's fun to use. That's always a good option too.