When I was at Winter 4x4 Jamboree in St. George this January I had several people ask me about my Oztent RV2 that I use for my display. My answer to everyone included I don't sell them but they are an awesome tent. The tent quality is great and it really can be setup in 30 seconds (basically). The bag is a little lacking and the strap can be improved (and has been by me, check the store) but overall it is really nice. People walked around and said, "We have been debating getting a roof top tent." Since I have grey in my beard and hair, its ok for me to say this, these statements mostly came from "older" couples. I have a Tepui Ayer that we have used for over 5 years, other than upgrading those pesky straps it has been mostly trouble free. It is great to stay up off the ground, but that leaves the downfall, climbing that ladder in the middle of the night, and scooting backwards thru the tent to get to said ladder. With ever greying hair that becomes a little more difficult each season. We leave our Ayer on our trailer so basecamp is always our choice, which leaves an Oztent as the same situation, if you are thru-traveling then the rtt makes a better case for itself but 30 seconds (or 2 minutes) isn't really that bad either, and you have to fold up the rtt also. So it comes down to physical capabilities and desires, for us its nice to have both and sometimes use both at the same time.
My prognostication for the future, just as Roof Top Tents started gaining traction in the United States a decade ago, I predict the Australian influence and the greying of us all, will lead to an expansion in the easy up high quality ground tents, like Oztent, Kodiak, and Gazelle. The good news is used rtt are still valuable to the younger overlanders so if you choose a rtt now and "age" out of it, someone else will gladly take it off your hands!