The Cursed Sword of Shagganuthor is a dark Twine short story casting you in the role of a villager participating in an uprising against an evil sorcerer-king.
The writing is extremely fine, and the central horror conceit is original and memorable. Chances are, it will stay with you for a while.
As for downsides, I will refer to Gijsbers' review: the story is so linear, it barely merits the interactive format. For much of the plot, I found it justifiable as an expression of the fatalism mentioned in the game blurb: the protagonist is swept along by events outside of his control, first in the battle, then by the effects of the curse. Even so, I found the linearity too overbearing: there are events that the protagonist should realistically be able to influence, but the story won't let you.
Also, while I've mentioned that I found the conceit original, the larger storyline of the curse is less so. Perhaps it's just that I read a lot of horror, but I still found the overall story predictable. Sometimes, predictability can add to horror: the inevitability of classical tragedy. In this case, however, I didn't experience that effect. That said, I wasn't expecting (Spoiler - click to show)the protagonist to infect his wife and father-in-law, rather than killing them.
A bit where the storytelling felt unclear: (Spoiler - click to show)when the protagonist proceeds to his father-in-law's house, I assumed that he would kill his father-in-law, and thus the man showing up alive later confused me a bit.
In short: brilliantly written, with some gruesomely original imagery, and well worth a read if you're a fan of body horror and dark fantasy. It just feels like it could have gone deeper.