Just now added about 400 new words for the easy difficulty and about 300 for hard difficulty.
This is because a couple of people said that this was the one change they wanted. It's pretty funny from a development point of view because it's the easiest thing to add. In fact with pretty much all the content that I've made so you can import your own, it would have been way easier to just add it myself than try and make it work with custom assets. For example, adding these words took at most half an hour, whereas adding the ability to add your own words took the best part of a day (and would have taken longer if not for having already spent easily more than a week full time on the importer).
I did it this way because, even though it meant I had to do more work, I thought people would enjoy being able to use their own stuff too. That's why I focused the rest of my time on things people wouldn't be able to add themselves - the interface, gameplay options, and game modes. I was so concerned with making the complex parts work well it never occured to me that the one gripe anyone would have would be this.