Hi Callum,
I'm not anticipating much changing in the TextRange module but I do need to dedicate a bit of time to just getting my head back into the code and finishing it off. The alpha tag is a deliberate safety net: I'm uncertain about decisions I've made, the complexity of the whole module and the fact that I haven't used it in any real projects yet. However, you were asking about the API, and I can't see that changing significantly. Using an options object as a parameter for most methods means there is plenty of flexibility for adding new features later.
Hope that helps. It's a pretty vague answer, I know.
Thanks,
Tim