N9YTY  Free until they tire of no getting money and call Intel Macs a new "platform" like Windows an get you to cough up another 15.  
(Version 9.2)

MARIO LEONTI  I have used Harmony since the early 90s. Since I bought it I NEVER paid 1 more cent for upgrades: they are all FREE forever. That's service!

An invaluable tool to composition and a recording studio, I have found Harmony excellent in every respect and the developers very responsive both to support and delivery. The new sound base (Gold) is worth buying too!.  
(Version 9.0.4)

ANONYMOUS  Harmony assistant is simply awesome both for features and price. Documentation is excellent and so is the web site. Highly recommended. Get GBMidi and the score can be directly imported to Garage band as midi.   
(Version 9.0.2)

THOR  Great update! The interface continues to improve (still some minor cosmetic glitches).

New installation process works great (No more installing into ~/Applications).

Can't wait to see how I can use this with GarageBand!!  
(Version 8.4.2)

TCLARK  Purchased through Kagi and I got my license string the next day. Everything works as advertised under Mac OS X 3.2 This software is a GREAT value. It is packed with features at a phenomenal price. It is good for composing in the classical sheet music tradition. It is also great for practice exercises with complex rythms which can be hard to decern with some sheet music. It will loop play any number of notes or measures. It can be better than a metronome in getting those rythms just right. You can't go wrong trying their demo which has all the features except saving your work and printing.   
(Version 8.4.1)

TSALAGI  This is a great low-end music composition and midi sequencing program. For OSX, it is about all there is for those of us on a budget. It lacks some features for midi-sequencing, but it also has some unusual features, like auto accompaniment.

The worst thing is that their kagi link for the U.S. does not work. I took a chance and purchased it through the European portal. Haven't received my registration code yet, so I'm crossing my fingers.  
(Version 8.4.1)

SAACIPLANK  Well, lets just say the best just got better. Its cheap, its easy to use, and it has so many features you wonder how it costs only $65! You have to try out this program.  
(Version 8.3)