We have had our Haven for a couple weeks. We haven't had any really bad weather to give an in depth review, but here are my observations:
Rog felt that the angle of the vestibule line was a bit steep to hold up in wind and I fully agree. Since the sides are steep, wind pressure will tend to pull up on the stakes more than push down on the poles.
We had one night where the forecast was for strong gusts, rain and hail so I did my own simulation and found that even 9" Easton stakes, in firm ground, at 45 degrees, pulled out easy with pressure against the vestibule. This is easily remedied by adding another line attached to the included top loops and extending at least 3 or 4 feet away from the shelter.
I don't think this is a bad thing, it is the price you pay for having the reduced footprint. In fact, I find that it just barely fits most of places I have pitched it. Most two person shelters wouldn't fit the sites we have used.
I suspect that the Lunar Duo wouldn't have fit because of the angled vestibules. I can see why Ron went with the steeper wall design.
Note, in this picture the added lines. This really added to the ability to withstand winds that night:
I am normally not a fan of double wall tents. The Haven is the exception.
First, the outer can be pitched first like many European double wall tents.
Second, with the vestibules open, it has as much, if not more ventilation than the inner screen alone on most double wall shelters, but can be closed up from inside the shelter if rain should happen in the middle of the night. A major improvement over most popular double wall shelters.
About the inability to fully close off the vestibule so that there is less of a gap at the bottom? Luckily Ron has more sense than the people making this request, by making sure that you can't fully seal off the shelter. You do have to breath and you don't want to close off the whole tent to hold in warmth.
The gap is what I would consider the minimum and feel that he really thought about this issue in the design. If you don't have enough ventilation, you won't sleep well and it can actually be harmful. Get your warmth from your gear, not by blocking off air flow.
This shelter will pitch tight with some experience. You probably won't get it right the first time. Practice makes it a lot easier after the first pitch or two.
I will try to post more of my thoughts as I get more experience in rougher conditions.