Give one, get one
Feedback Exchange
Post your app — shipped or still in TestFlight — get honest product feedback from other developers, and give feedback back. The people answering ship apps too; they spot what your friends politely don't.
Product feedback only — never App Store reviews. Trading, buying or incentivising App Store ratings and reviews breaks App Store Review Guideline 3.1 and the Developer Program License Agreement, and Apple removes apps and terminates accounts over it. Everything posted here stays on Appstro. Don't ask anyone for stars — report anyone who does.