Yea great question! So yes, I used Second to build the foundation, auth, and DB stuff (starter plan stuff). But other parts of my app have not been ported back into modules yet (which will become Pro modules).
At some point I want to do a full rebuild of Second using Second to test out all of the modules together. But I'm not quite there yet!
If yes, where has it been useful, and if not, what does it not handle well?