No. The converter doesn't exist. I don't think it even can exist yet since QUCS doesn't support 3rd-party libraries at the moment (see their roadmap). You are limited to the components available in QUCS.
So to build a converter, you have to make sure that your design only uses components available in QUCS and then map it over. That will involve translating the coordinates of all your wires and such (you may have to reroute some of the connections in the process). It isn't all that trivial of a task.
The converter now exists:
It substitutes custom gschem symbols *-QUCS.sym that match the QUCS device geometries. You will need to put these symbols in your gschem library search path.
The converter also does LT-Spice .asc -> gschem conversion in a similar manner.
As for "and what does it get you in the end?", it sure beats duplicating a design that's been modelled if one wants to get started on designing a PCB.