I worked with the EDJ disciplines several times over the course of the years.
...and I'm very much disagreeing on the relative power of the Combat Mage. I spent years trying to improve it, and even now I'm far from feeling its complete. The recognizable balance between 'combat ready' spellcaster (as a wizard no less) and the ability to engage in melee combat is both a strength and a very large achilles heel. I am mostly looking forward to seeing how the new disciplines transition into 4th Edition before I tweak it further. If any of you are interested in checking out where my evolution of the discipline has gone, you can find it here: http://www.earthdawncompendium.com/disc ... a76a000002
Mystic Warrior was a very nice addition. We had few problems using it, though with some added tweaks we picked up from the Pugilist from Cathay, it really rounded out in our games. If any of you are interested, that write up is also here: http://www.earthdawncompendium.com/disc ... a76a00001d
The Spy I worked with once, can't really say it was anything special that you couldn't do with any other class just played AS a spy.
Songsmith was a nice addition to our group when it was being used, but I think this had more to do with the player than the actual discipline.
I fell in love with the Taildancer on first sight, and continued that affection even when it went through its evolution with 3rd Edition,and IMO its better now than it ever was.
The Inquisitor is one that needed the most tweaking, but was by far and large the most successful thing we ever added to our particular group. There are also several other variants that were around the web at the time of its creation. However, my version is posted here as well. : http://www.earthdawncompendium.com/disc ... a76a00001a
Not sure how backwards compatible friendly they may be to the OP. The originals can be found pretty easy on the web if you are so inclined to dig.