Shared decks versus writing your own. The most persistent argument in the medical communities. Shared decks are enormous, well-maintained and save hundreds of hours. The counter-argument is that writing the card is where the learning happens, and that a deck sized to a whole discipline buries what your course actually covers. Both sides have a genuine case and the honest summary says so.
Subscription fatigue. Recurring and increasingly heated. The specific complaint is less about the amount than about losing access to material you created when you stop paying.
Backlog guilt. Cards pile up, the number becomes intimidating, and people abandon the app rather than face it. This produces more posts than any feature request. Worth addressing properly, since it is a genuine problem and the usual advice, do not reset, is correct but unsatisfying.
Settings paralysis. Long threads about optimal intervals, retention targets and scheduler parameters, usually written by people who could have been reviewing. There is a self-aware strand of the community that says this outright.
iPad and handwriting workflows. Growing, driven by Apple Pencil use. Notably underserved by the main apps, which is why the discussion tends to be about combinations of tools rather than one.
Card quality. The consensus that badly written cards, not bad scheduling, cause most failures. This is the one point almost everyone agrees on.
Once, near the end, in a short paragraph. It should read as a disclosure rather than a pitch: built by one person, Apple only, no shared decks, no audio, has a scheduler and a drawing pad. Then a link out and nothing more.
The page earns its ranking by being genuinely useful to somebody deciding. If it reads as an advert wearing a Reddit costume it will fail, and it will fail loudly.