Currently use QC to make custom layers for Bonix TV - a vision mixing kind of application for OS X with a kind of QC stack of layers, each layer being a composition with published ports and some protocols for data types. Also generate sports graphics and twitter feeds and so on for video score boards at large sporting venues.
Spent a few years learning Quartz Composer as my way back into coding from a decade away doing design related work. Film, graphics, studied Architecture for a few years and got involved in publishing then film. Now moving into front side web development. Hope to get into app dev with Vuo and rapid app prototyping.
p.s. I started with Basic too, reading the printouts of the source code for Adventure game and Start-trek running on mainframes got me into fortran and pascal soon followed (real functions and line numbers became optional, Yay!!).
Every app I've made, the first request from the user is always, "Can you make it so it opens in the same place as when I closed it like every other Mac app." It's a real pain having to add all the nodes necessary to achieve this and it is really spoiling my enjoyment of the product.