I use Harmony Assistant, which is the 'big brother' of Melody Assistant. The current version of Harmony is 8.0.5 and seems to be very stable. I have found that the stability varies a lot version to version: the last version of the 7 series was much less stable than the preceding one. One of the most off putting things about the first version of the software I used is that it opened every available toolbar at once and there are about 30 of the things. The first task is to close them all down without looking at them too much and then only open the ones you need. There are about 4 I normally have open (notes, rests and play are the main ones).

I haven't used Noteworthy much - I did an evaluation exercise a few years back before settling on Melody (and later upgrading to Harmony). The big plus for Melody is that it handled ABC, which at the time NoteWorthy didn't -does it now? Coupled with ABCMUS, I can easily read anything out of the DT and begin manipulating it, which (at the time) I couldn't do effectively with Noteworthy, since the only option was to go via a MIDI which lost even an attempt at the lyrics.