nikon d90 for me.
I think it would be more interesting as to why people went with what brands. For me I didn't like the canon's felt in my hand.
Ditto on that. I liked how the d90 felt in my hand vs. the t1i (at that time). I'm glad I chose Nikon.
When I was in photo school, I snagged a really good deal on an old Mamiya 645 1000s system. It shot medium format film, in the 6cm x 4.5cm format. With an optional handgrip that had a strap that wrapped around the back of the hand, it was dream to shoot handheld. The system came with nearly 1/2 dozen lenses, plus a motor drive, extra film inserts, view finders, etc etc.
(For those who are unfamiliar with the Mamiya 645 system - everything is modular. You can put anyone of at least 4 different viewfinders on it. The film backs (in the generation after the 1000s) were little light tight boxes. So you could load as many rolls of film as you had film backs. When you finished the roll you popped the film back off, and popped the next loaded one on.)
Eventually I had the Polaroid film back, and added to the lenses including an 80mm shift lense. etc etc. The 110mm lense (about a 90mm lense in 35mm film camera terms) was as sharp as a Hassy lense. The 645 film format was, iirc, about 3x bigger than a 35mm film format.
Eventually I needed to go digital, and I had this great collection of lenses and other funky stuff for the Mamiya 645 system. So I went with a digital system that allowed me to move over as much of my stuff as possible. The glass is not perfect for the sensor - but at least I've got something to work with while I upgrade the glass. Besides - it amuses me to use lenses that are now 20+ years old on a cutting edge digital camera.
PhaseOne and Mamiya are working hand in hand, so the old Mamiya stuff works with the PhaseOne body.
So - that is why I use what I use.