We demo'd one at our dealer's demo day back in the spring. I think the rear discharge would be great on large area commercial properties, cemeteries, municipals that don't really care about the looks as much. I don't know about others but I could definitely tell a difference in cut after appearance with the clippings on the rear vs. being blown out the side. I wouldn't use it on residential lawns that care about that "exmark" cut.
This was on a 60" DS too. It's a beast of a mower.