I have one of these, not for sale, that I've used extensively.

Only a few drawbacks.

1. In a not too high wind ~20MPH+ it presents a big sail area and
will wrap around the top of the van unless you stake down the support
frame to the ground.

2.  Clearance in the sliding pieces that form the rigid roof frame is
limited and if they bend at all (due to a instance of 1 above) they
are irretrievably toast and 140$US to replace and reinstallation is
a major job.

3.  The little locking tab that secures the system together when retracted
is unbeliveable flimsy as it fits into a little channel in a plastic end
piece that if not properly seated when retracing the system can snap off.
This item is not replaceable without a major overhaul of the awning.

4.  Other than that, Mrs. Lincoln, it was a fine play don't you think.
    The Transawn/Catalina 2500 are quite useful but watch the wind issue
    and in windy spots don't leave it extended whilst you wander about
    the scenery.

5.  If you use the attach-to-vanagon-body mounts the wind problem remains.

Really fine in desert,  rain, snow (tip downward to make a self shedding shed)
overly complex for what it does though.

al