I jumped from Nikoin to Sony about a decade ago for reasons that are probably still pretty accurate (consider the dual slot comments above)…I had a Nikon D50 and wanted to upgrade or jump brands. Nikon had an ‘artificial’ segmentation in their product line where the moved the motors into the lenses and only the more expensive bodies had a motor to drive older/non-motorised lenses. I didn’t recall caring for the Canons at the time, but don’t recall why.
Sony, on the other hand, had an EFD eyepiece, a motor in the body (which drove the long-zoom lens), and did so 10-15% cheaper than Nikon and Canon…the impression was that the established brands were gaming the system and Sony was hungry for new customers.
The fact that the sensor was the same in all of their bodies at the time and that they manufactured 90+% of the sensors for the phone market didn’t hurt either (experience + economy of scale)
The only real downsides I’ve seen with the a57 I bought are an occasional reboot needed to restore sanity, the main display coating is peeling off, and the ‘50 prime equivalent’ lens was about twice the cost of Nikon and Canon. The quality has been AWESOME…allowing me to take the kinds of photos that look like someone much better than me could take.