The Strymon Deco reproduces the various tape effects created by the manipulation of tape in dual recording units, inspired by the recording breakthroughs of early greats like Les Paul in the late 40's - early 50's. To be honest, although I found the concept interesting, I wasn't particularly excited about this pedal until I began to play it.
In addition to a beautiful and touch sensitive tape saturation, the Deco can be used to produce an extremely natural and warm sounding tape flange and slap back delay. Taken a step further, the Deco can fatten your signal by doubling your guitar; or it can trail out in a dramatic short echo that fills the space on lead lines. It sounds great on its own, but to me where the Deco really shines is paired with a drive. The tape saturation adds a hint of compression and slickness, while the record and lag decks add a three dimensional depth to your tone.
I think it would be easy for your average player to overlook the Deco. "I have a tape delay, and I don't ever use slap back. What's the point of a doubletracker that doesn't actually record and loop?" I myself was dubious of this pedal until I got to play one. The tape saturation side is the only "always on" you need. At subtle settings, it adds feel and responsiveness. At a more drastic setting, it provides a natural low gain that brings out movement in the doubletracker or other effects, and responds with a growl when you dig in; but is completely clean when you want it to be. Plus, the momentary switch for the flanger is genius. The doubletracker adds new life to simple guitar parts, and new tonal depth to your dirt and fuzz pedals. Filling empty space and sitting perfectly in the mix, it glues your guitar parts together and is endlessly fun to play with.