I bought one (the Sony A73). For me, low-light performance was the big draw vs sticking with a cheaper crop sensor. I'm just a hobbyist photographer, but I kept

I bought one (the Sony A73). For me, low-light performance was the big draw vs sticking with a cheaper crop sensor. I'm just a hobbyist photographer, but I kept getting disappointed by things like an indoor family gathering where if I didn't want to use a flash, I had to bump the ISO up to super-grainy and drop the shutter speed lower than what my kid can keep still for. With the A73 and a nice prime lens, I can go all the way to ISO 6400 with perfectly acceptable noise levels, and thanks to the great dynamic range, bring the shadows up further at my computer. It allows me to capture certain scenes that would be hard to get a "keeper" from at all on a crop. For well-lit outdoor photography, including sports & wildlife, I agree that the gains over a high-end APS-C are marginal. Even for portraits, the bokeh on a full-frame is going to be better, but it'd probably be fair to call it marginally better.