I've had one in continuous use (along with the OCD) for a few years and it never disappoints. The FD-2 is very flexible and, importantly, is capable of preserving the transparent sound of your guitar and amp when desired. Not that I put much weight on anything Guitar Player magazine says but, rightfully so, the FD-2 was heralded as one of the best stompboxes of all time. I think it actually does live up to the hype because it does so many things well and nothing badly.
By the way, if you're wondering what the heck 'MOSFET' stands for, it is short for Metal Oxide Semiconductor Field Effect Transistor. Now you know as much as I do.
I'm not a fan of everything Fulltone puts out; I was emphatically not a fan of the Fulltone Catalyst (Failtone) but the FD-2M really stands out from the crowd even though it wears a mass consumption price tag -- don't let the lack of 'price prestige' fool you. For sure, if it ever even enjoyed boutique status, Fulltone has all but lost anything remotely resembling that image (they're available just about everywhere, including all the big online retailers that cater to the unwashed masses), nonetheless, the Full-Drive 2 delivers great sounds, it's built like a tank in the USA, is very affordable, and it warrants the Psychopompos recommended best buy.