I've owned piles of their markers, a few of each model, though now I'm down to two Diadems (one kit gun, one DITS) and two Sentinels.
Their takes on existing designs did two things; they improved the efficiency and general functionality of the gun itself, but they also brought (at the time) high end features and upgradability to low/midrange marker platforms which were otherwise too expensive or functionally impractical invest in long-term. Their standard marker, the Sentinel, was an STBB (think Spyder) but featured Autococker barrel/ detent threading and Angel feedneck threading as well as a delrin bolt, and could be upgraded to a FASOR (think Infinity Legend) by purchasing and installing a kit.
The best feature of AM guns are the "tweakability" - you can adjust the HPR pressure and the rear IVG like most other markers, but you also have control of the cupseal spring via under-barrel adjustment points. The second best feature was that every model looked good out of the box - neat Tribal milling and quality anodizing made them more than your typical low/midrange brick, tube or series of tubes.
Illusions are amazing; almost like an SS25 conceptually, part Spyder, part Sniper, and smarter than the two put together. Dual AC detents, Angel feedneck, dual pump arms, delrin pump handle, delrin bolt, delrin wrapped hammer, and a crisp swing trigger - not to mention the optional stockfeed. Shorter, lighter, and far more customizable than other stacked-tube pumps of its time. It was no more an "autococker" or "sniper" than an AKA Merlin or Azodin KP is, completely different specs all around, but that didn't stop K2 from threatening them... that was not the only reason they withdrew from the market, though.