I like to keep track of new notation/engraving programs, and here's an interesting new one: Nihavent. It's designed immediately for notating Turkish maqam and microtonal music with appropriate accidentals and accurate playback, but the structure of the program, as a whole, even in this beta version, is very promising for general use. Among other things, it may well have the easiest learning curve for any notation program available, with the seven page users' guide all you really need to get started; I was able to compose a small piece on screen immediately after opening the program for the first time. [As a bonus, AFAIC, I was able to enter time signatures with non-powers of two denominators — 2/3 or 6/5, for example — and not only to space and print correctly but playback without a hitch. Henry Cowell would have been very happy about this!]
This is a beta version and a number of additional features will be required to make it competitive with well-known general-purpose professional engraving programs, but it's a great start and — for maqam and microtonal music — already a serious player, offering capacity out of the box that the majors don't have without serious kludges. I recommend testing the program and am curious to see if this can developed, with feedback, in more useful ways for new music.