I've recently finished reading Past Sins, by PenStrokePony. And yes, that includes the three sequels in the series and the 'interquel' during Nyx's first few hours of life. I've never been much on reading, only finding that I read most novels during English class back in High School (Parvanna, The Outsiders and Raw just to name a few). This series, however, is one of few that really got to me. I adored Nyx's character and her involvement with Twilight and her friends and family, and I've really enjoyed the story-telling. I even found myself ducking into the bathroom or taking slightly longer than normal during breaks, just so I could lose myself in the plot.
To me, Past Sins will always be something special and I truly do hope we see more of Nyx from Pen Stroke. But if he doesn't continue the story of Past Sins, I feel he ended the series on a very strong note. Nyx has become one of my favourite characters in the MLP fanbase, and seeing her grow and develop in this series has been a great and enjoyable experience.