@stonysmith regarding your questions:
1. It can definitely scan other than humanoids. They also provide an app named "room capture" but haven't used it yet (I only own this sensor for less than 2 weeks).
Here is a capture with the structure sensor (totally un-processed):
Ceramic cow
Same object with 123D Catch (processed):
Ceramic cow
maybe, planning to find out.
I don't think so. You need to walk all around the building in order to scan it. You should also keep the building "framed" in the iPad to do this, so I don't think this is an easy task.
According to Occipital (the company who makes the Structure Sensor) small objects are difficult to scan and may not get scanned correctly. However, even if I haven't scanned a small object yet, I think it will make it.
There are 2 different ways to scan. 1st is to use their native Structure software with/or without Scannect (for color scans). 2nd is to use another Occipital's software called itSeez3D. In my opinion, one can get better results by using itSeez3D in terms of color quality.
By now, I can only compare 123D vs Structure sensor, so I think that the Structure sensor is better in terms of accuracy too. However, I wouldn't say that 123D is useless compared to the Structure sensor, as Autodesk is keeping their software under continuous development and they come up with better results every time they release their new software version.
That depends of the scanning time. You can scan an object only by making a quick walk around it with the iPad, but you can also come back again and again to improve the scan. That makes the result high or low polygon, also more accurate or not (this is only when using their native Structure software, not sure yet if this works with itSeez3D).
I can give you both cows that are listed above, (the source scans so you can compare yourself). Keep in mind, that the both cow scans, were scanned under -almost- the same environment, while I took and lots of photos for 123D Catch and shot VERY carefully, (I did it in order to avoid post process).