I have spent some time manually entering people. In general, I think the current UI is very clean, but I have a couple of suggestions:
1 - Adding a father via the pedigree page - It would be more convenient if the Last Name field was prepopulated with the last name of the person you are adding.
2 - I think it would be more intuitive if the forms for editing a profile were about the same as the ones for adding a new person. I noticed this after typing the wrong birth and death dates for a new parent, then finding that the flow for editing the profile was very different for updating those same dates.
2a - the use of radio buttons for replacing the existing data was not clear to me right away either (I confess to not watching the video first), but once I figured it out, it seemed natural. Something tells me that the radio buttons will be very useful when you are merging in new facts later on.