I'll simply post the link to its beta / thread on kvr:
Basically, Architect is a modular MIDI sequencer halfway between max and Numerology. And soon with an optional tracker-interface (according to its dev, it's almost done but needs some polishing).
I'm simply blown away by this thing. Just give it a try really, it's incredibly intuitive, deep and flexible. Dead-stable and mature too.
I barely ever use audio during production and am seriously planing to use Architect exclusively soonish. I'll still mix using Reaper I guess, but as I've always wished for a sequencer that would combine what I like in Live, Numerology and Renoise, I feel like it's the right tool for me.
From what I've gathered reading the aforementioned Architect's topic, you should feel right at home if you're experienced with max and/or PD.