The voice understanding is impressive, but obviously a video can show the best-case.
The factual questions themselves aren't hard. I've written a toy QA system, and it could handle the base case of those - they are just straight querying on Freebase/DBpedia.
The longer question ("the population, land area and capitals of Japan, India and China") was good.
If anyone has a working copy, I'd like to know which of these it can handle:
"Who is Bill Clinton?"
"Who is Bill Clinton's daughter?"
"Who did Bill Clinton's daughter marry?"
If it can get the third level then it's pretty good. From memory something like OpenEphyra can sometimes get that 3rd level, but usually fails.
I thought the contextual querying (where one query led to another and it had to remember the previous details) was pretty good.