I've not had success with actually adding a feature. It works up to that point (choosing the feature type), but clicking on the map after that point does nothing.
Looks like an issue with the proxy from where the sample is being hosted. I ran the sample code locally and downloaded the sample proxy page from here and it seems to work fine. Can you run it locally and tell me what you find?
I've downloaded the html file, edited the url of the proxy page to point to my proxy page and ran it locally. The basemap loads but when I click on "add" it brings up a blank grey page (except for the black header). I've just checked the url for the feature service that is used:
and it says "invalid url". I guess I'll try to create my own feature service to get going with this but it'd be nice to see a working example first. ESRI - any thoughts as to whether the above feature service will be sorted or not?