For me I actually spent a fair bit of time trying to decide what machine to get, after my iMac died. What I went with is a docked 15 inch MBP (16gb ram, 2.5ghz i7)

Display's on desk are an HP 32-inch envy (main) and portrait 24 inch dell p2414 (secondary)

Mouse is logitech m705, keyboard corsair mechanical keyboard

dev done in virtualbox linux VM, which i definitely recommend doing if you can get away with it.

I will likely move to a linux machine next time around, short of apple surprising us with a new release.