I have seen one in use and talked to two owners, but I don't have one. While the design is well done, I would not want to have one.
The width of the bike (riderless) plus side carrier is acceptable (69,5 or 74 cm + 2 cm for the bike tire – 27,4 or 29,1 inches + 1 inch), the practical width is more like 100–110 cm (40-44 in) when you take into account the width of the adult cyclist. So the Side carrier sounds interesting on well groomed multi-use paths without bollards or other similar obstacles, but not in traffic nor on paths with obstacles (i.e. most paths around here).