First off, I LOVE the Harlowe story format. It's really helped bridge that serious code obstacle that stops me as a writer producing highly effective interactive fiction games.
In fact, I'm currently using Harlowe to finish off a dead game project I was part of, where the team just fell apart. As the writer for said project, I had a game script of 400k words just lying around, and since I'm not a coder, it was just sitting there gathering dust. Harlowe is letting me produce an actual game from this script, so thank you so much.
That said, there's one big potential obstacle I can see if I do complete this game. As I understand it (and I could be wrong), Harlowe has the ability to save, but it's stored in the cache related to that specific site. So if you were to play the same game in a different location, the save wouldn't carry over. Or if you downloaded the HTML and you'd been playing it on a website, it also wouldn't carry. Also, if you deleted your cache, you'd lose your savegame.
If this was a short game, it'd be no problem. But since it's a very long game that would involve multiple playthroughs, it's a real stickler. I think Sugarcube has this functionality, but to be honest, Harlowe is so user-friendly I'd be highly loathe to switch story formats.
I guess my question is this: is my understanding of the Harlowe save mechanics correct, and if so, are there any plans to expand Harlowe's save ability to allow saving and loading to a file?