Harmony Assistant is a fabulous piece of software. It is a staff-centric composition tool, definitely geared toward musicians who read, write and prefer Standard Notation over tapedeck/pianoroll/drumbox metaphors. The vocabulary of notational devices is immense. Clefs, staves, tablature, tuplets, the works. Print quality is fabulous. From a simple guitar-chord + lyrics arrangement to multi-stave orchestral works, it produces great results.

The number of features is very impressive and it is quite customizable. It offers auto-accompaniment in addition to that creepy synthetic vocalist. Interfaces really well with Reason, too.