As an added benefit, you get integration with Outlook Tasks as well, if you use this on the desktop. Anyway, the Cortana integration with Microsoft To-Do is only available in English in the UK, Australia, India, the USA (of course).
Some typical things you can use your voice to ask Cortana to do now that integrate with Microsoft To-Do include (screenshotted below):
"Add 'Pack my iMac' to my To-Do list"
"Remind me to set off for Hatfield at 8.30am"
Pretty cool to see all this joined up thinking from Microsoft, if a little belatedly, some might argue.
The next major Microsoft To-Do update will hopefully see file attachments on tasks, which will turn the application into a genuine mini-project manager. I can't wait.
Comments welcome on this new Cortana ability - obviously this is a case of Windows 10 Mobile inheriting extra functionality from its Desktop and ecosystem-wide sister platforms, but it's very welcome nevertheless. Hopefully it'll be available in other languages and regions in due course.