In the summer I certainly appreciate why people want a double walled shelter. They certainly have a lot of comfort features going for them. There are certainly double wall shelters that are in the said weight league as some of the more feature full tarptents... but there are some ultralight shelters which are significantly lighter. For example, I have been using a zpack's hexamid since late Jan. The shelter + groundcloth + stakes is 12oz.. plus an additional 4oz for the hiking pole I would be carrying anyway. There are no double wall shelters that get quite that light,

In the winter, it is good to have a shelter which fully blocks wind and keeps blown snow out. 3 season shelter and tarptents are less than ideal because they don't do this. They are designed to ventilate which is what you want in the other three seasons.

Can you use a 3 season shelter in the typical mid-west winter. Yes, it's possible, but there I have also occasionally had an unpleasant night when we got dumped on with powdery snow and strong winds because the snow came right through the mesh. When I really expect snow I switch from a tarptent shelter to a classic floorless pyramid tarp which I stake down to the ground.

--mark