Is this lightweight?

Their singles and doubles are super light. Just pre-ordered their double

At what point do you transition from hammock to tree house?

I think you will be better off with the Warbonnet Blackbird. The hammock you listed doesn't include a bug net.

HYOH

It looks like a fun summer backyard thing, but not for camping. I don't get it. Why would you want one?

I think the size would limit the campsites available, which is just what a single hammock helps to solve. I think it would be hard to tension evenly with trees at less than square intervals.

How would you insulate each sleeper?

Bugs?

One person getting in and out would wake the rest– like a spider web.

Tarps are usually hung on a center ridge line in some sort of tensioned a-frame. I don't see that opportunity with this one, leaving a huge lean-to which won't be good in the wind and probably trap a lot of water.

$395 is a lot and I can imagine what a Cuben tarp is going to cost.

Sleeping with multiple people on that would be like trying to make love on a water bed (says the refuge from 70's).