Fan made content is usually way too raw to create an enjoyable experience for me, but ST Horizon definitely sets itself apart and can stand on it's own even by regular standards. The production value is pretty good and I even liked their cinematographic choice of using blur and lens flares to hide imperfections. It may not be everyone's cup of tea and needs some time to get used to, but I think it's better this way than to have distracting green screen sets like they used on Sanctuary (TV show). The acting is also decent, Lang carries the movie quite well and Bussell, Thompson and Kaiser deliver performances around him that really feel like a genuine effort. It still is a bit flat at times and the movie had a few difficulties to evoke emotions in me, but it's absolutely no cringe-fest like lower quality fan content.
The story itself is also very good, there are a few flaws in the plot but it's still rock solid and made the movie for me. I got hooked right away and was thoroughly entertained by it. Some of the dialogues could have used some polishing, but that would be nitpicking on an otherwise great experience.
Overall, I can highly recommend the movie to fans of the franchise.