I dropped by the EarthCruiser shop in Bend and looked at the GZL on a Tacoma with beefed up shocks and springs. They are still working on details but the basic unit is impressive albeit expensive ($30k+). It looks very European both inside and out. They plan a few changes better suited to the American market and to reduce weight (around 750 lbs dry).
The top is relatively easy to raise and lower with piston assist. The pop-up sides are soft but well insulated and have several adjustable openings. I think winter camping would be comfortable.
The dinette is big enough to seat 4 and can be converted into a bed, so it is possible for a family of 4 to travel. The table can even be moved outside. However, the limited storage and truck payload make it more likely for this to be suitable for a couple. The storage consists of many small cubbyholes--I counted 15--and shallow cabinets with some additional space under the seats. The cubbyholes are covered with a thick, flexible fabric to keep stuff in place, although I'm afraid I could never find anything with so many places to look!
The bed slides out to a north-south direction with your head towards the rear. I found this arrangement to be very awkward in the XPCamper V2, and the GZL is similar. That alone would keep me from considering this camper although it might not bother some people, especially if they are alone.
All-in-all my impression is that the GZL is a strong, compact, high-end unit that should carry well on a mid-sized pickup. But perfection doesn’t exist--definitely not in campers--so you have to decide if the layout and cost work for you. If so, the GZL would be a great choice and is backed by an experienced company.