Personally, my list of cameras has been (thankfully) a short one. The expense of each "upgrade" has been a hard pill to swallow, but I think my decision and thought process was well researched.
My first camera was the Olympus OM-10. A very nice manual SLR which had a bit of automation built-in. Mine was purchased second-hand from a shop in Misawa, Japan and (regretably) had a pretty nasty metering problem wherein no matter the shutter speed, the camera would act as though set to a shutter speed of several seconds.
This lasted until my pizza job (I was in high school) allowed me to get one of the newly released Canon Rebel kits. I shot photos throughout northern Japan, and later (when I was in the military) Germany, Saudi Arabia, and Bahrain. When that camera started showing its age (prism damage, etc) I had to upgrade again.
While researching options, I looked at the offerings from Nikon. I wanted to get a digital SLR but the costs of what I wanted were too far out of reach. I didn't want to get a "consumer" grade DSLR - I wanted rugged and weather resistant. I had learned that the environment was -hard- on a camera. The D200 was the rock I was after - its big brother, the D2X, was much too costly. Unfortunately, the price of the D200 was, itself, out of range. That brought in the N80. Film based, yes, but rugged (to a point) and it banned what I called the "amateur modes" (you know, the little icons of shooting modes...) It was the "pro" camera I could afford.
When my situation changed and I could get the D200, I made my leap into digital and bought my "baby". It has all the features that I was looking for including the rugged construction and the "can't-live-without" vertical grip w/ shutter release.
I do all flavors of photography (not necessarily good) - landscapes, portraits, street, candids, photojournalism, etc. Because of this I stocked a range of Nikkors from a 24mm f/2.8, a 50mm f/1.8, and a 70-300 f/4.0-5.6. My choice between Canon and Nikon was a practical one - I had Nikon glass and could ill-afford the transition to Canon.
My Canon Rebel allowed me to take great photos. Similarly, the N80 helped me produce some fine slides. The D200 has been a learning environment for me. I know nothing at all about the digital darkroom. But I remember two things that brought me to this point:
1) Shooting roll after roll of Sensia and not having any keepers is a waste of money. Digital removes this true thorn in my creativity. My D200's monitor can tell me if my shot sucked or not.
2) Processing my own "film" and printing my "good ones" saves me money. I need only send big prints out since my Canon (true enough) printer can output 8x10.
Now, having all said that, let's talk about calibration...
Cheers,
Sean