Bigma and the K5

Nice shots. The K-5 is a wonderful camera and no FF is truly "needed" (as far as I'm concerned).

I do think it is important to remember that the DOF gets shallower the larger the sensor (or film format) for the same focal length/aperture combination. The opposite it true as you go smaller, which is why the Pentax Q is great for macro (get the whole bug in focus in one shot rather than a thin slice, as one would with a larger sensor).

So if you are a super shallow DOF shooter, the FF would be nice. But I think there are attributes that are much more important than the sensor SIZE to a good camera.