Ok, I’ve played around a bit with DxO and Lightroom. For your reference, here is yesterday’s image again.
If we ignore the different colors and looks, what remains is an effect that I find quite pleasing. Yes, we lose a little bit on the sides and at the top, but the result does indeed look much more natural.
Is it worth it using the fisheye along with DxO and some extra treatment in Lightroom over, say, the rectilinear 7-14/2.8? Well, probably not, but then, if we see it as just one more tool in our set, I think there’s nothing wrong with it. And yes, of course all those software tricks cost you some ultimate sharpness, but so do in-camera corrections. Do I care? Nope. Not at all.