I think with Allan the synthaxe afforded him the ability to play a wind instrument rather than a guitar. He says he's restrained by technology, it limits his ability to play what he hears in his own head. Allan always wanted to play sax, couldn't afford one, so he felt rather forced into being a guitarist. Funny that he didn't become a pianist since his father was a jazz piano player!!!
I do enjoy some of his synthaxe work immensely, especially on Secrets (my favorite AH album). Distance vs Desire from Sand is a very heart-felt expressive tune. Flat-Tire, however, requires too much concentration.
I agree about the amount of material being released by Allan lately is staggering, I haven't picked up "Then" yet, but I've heard it's awesome. With any luck the K-2 disc should be out soon.