I didn’t use any diffusers on the flashes. For all photos the flash was pointed up into the ceiling or wall/ceiling corner. The purpose here is to diffuse the flash and spread it way out so that, as you say, the rooms look friendlier and don’t look flash lit. To see what I mean, take a look at the towels by the window in the last photo. Notice how soft the shadows are around them? With direct flash you would see a rock hard shadow that would be the furthest thing from appealing.

Now, had I needed to use a flash firing directly into the room to fill in any shadows, I definitely would have put some kind of diffusion on it. A shoot-through umbrella perhaps.

Yes, the photos probably did a good job to entice them, but the place is nice to start with!

I had an agent try to list a vacant apartment that I had. She used her camera to take the shots. It was a P&S. It killed me to see what she uploaded, and I think that her terrible shots and camera ruined my chance for rental. We eventually got it rented, but not through her.

Good fortune with the new endeavor!
Scott