There are significant challenges as well in street navigation, where a robotic device would have to navigate, not only around static obstacles, but navigate where there is dynamic movement of humans (walking or driving) going about their ordinary business. This video provides one idea of how that might actually work in practice.
But navigation is only one of the difficulties mentioned here. There are still significant problems in other areas like the questions of safety and reliability mentioned earlier or, for example, how to achieve meaningful interactions in emotionally sensitive settings and activities that require fluent sociality. Many of the developments to-date point to flaws in the conceptualization and crafting of assistive robots for ordinary settings—that naturally occurring behaviours and activities of humans are not well understood or appreciated.