I am a wee bitty unorganized, aren't I? Sorry about that.
A MST is script format, though. Oof. Hope I haven't given you any wrong ideas here, or confused you so much that your head implodes and gorillas fly out.

First and foremost, I dislike it because it's easier to create. A person doesn't have to put as much time into it, which makes such things far, far more prone to being rubbish. A good writer will avoid that anyway, of course, but still, there is a great deal more pleasure to be had in reading prose, because it actually draws you into the narrative - it's literal storytelling, rather than the cold, clipped attitude of a script. That's not a story - it's the very detailed outline of a story. It's much harder to enjoy.

That said, there's nothing inherently wrong with it, but I won't read anything - fic, misson, whatever - that's in script format.

I can't speak for everyone, of course. But if it's a script, then script form is the way to go. One of my favourite Discworld fanfics was in script movie form. It's annoying when writers use script form incorrectly or in the wrong context though. A novel or a short story is very different from a play. It may be easier for you to write in script form, but it is difficult to read sometimes and you miss out on a lot of the description with script form. Personally I think prose is easier to read and write.

Also, if you don't care if your audience finds reading your story difficult, then you obviously don't care if they like your fic or not. Therefor, if someone complains about it, you shouldn't care about that.