I used it, because it gave some sort of multitasking, but I didn't ever suspect that it was somewhat of development environment.
A vast number of those went to developers so that they could e.g. run a compiler in its own window, until two things happened:
a) One of Quarterdeck's backup tapes vanished.
b) Microsoft brought out Windows-386.
I make no claim that those two events were related.
I'm afraid that I no longer have documentation or software catalogues etc., and my journalist friend- an occasional member of this forum- is hospitalised and in need of our well-wishes (a few decades ago I'd have unashamedly said "prayers").
There was a handful of companion toolkits, to present various types of pop-up information with a "look and feel" similar to the Desqview windows. I suspect that in practice these were TSRs, but possibly with privileged hooks into the memory manager to pick up hotkeys and/or background events. However the thing that sticks in my mind was the attempt at orthogonality in the APIs: somebody had tackled that with what can only be described as obsessive resolve.
The company with which I was associated /tried/ to build a business system using the underlying technology and primitive (NetBIOS over yellow-wire Ethernet) networking, but failed dismally because of what were basically "people problems": a Byte-reading MD to whom the idea of writing a specification was anathema, and his drinking buddies all pulling in their own directions.
MarkMLl