I figured I'd add some updated data to this thread. This week I flew ET in J with a 12 hour layover. Ticket was a United award. I was very impressed to see that, on check in in Harare, the agent had right next to her my hotel voucher. It was for the Hilton, and it included dinner and breakfast, which was generous considering I arrived at 9 pm and left at 9 am.

Doesn't seem that you need a visa for transiting, I think they just stamp your boarding pass. I had a visa, so just used that. All in all, very excellent.