I like this story! (Huh. I seem to say that about all Alicorn stories...) It feels much more about the characters (as opposed to being about the world) than Threshold, and (as Bluelantern said) it's got some good knife-twisting in it. I found myself really empathizing with the characters, even though I've never been through any of the experiences they go through. It was actually hard to read some parts, the depiction of their anguish felt so real. Powerful stuff!
I really like the Threshold setting (both characters and world) a lot - as you might expect, since I was the one who requested this setting - and I also definitely hope to see more of all aspects it! I want to see more of Lyle and Mercy's relationship, and Mercy's meeting with her father, and.. ahem. Sorry, I get greedy. It would also be cool to learn more about the history of the world, and to follow its progression forward. The impression I get is that, while uploading and such have matured pretty well, the technology as a whole is still rapidly developing. Society is certainly still adapting to it, and they way that's depicted (from what we've seen so far) is very believable.