It's hard to tell how widespread the problem is.
There are issues that are obvious, let's say laptop shutting down randmly or battery running out in 15 minutes instead of 5 hours. Everyone detects and reports those.
There are issues that are obvious, but the average user considers the normal mode of operation.
- No sound from iPhone speaker? I thought those are only for calls. I use headphones for everything. (personal experience)
- Dead pixel? What's that? I don't care for it. It was always there. I can still watch my movies.
- Wifi dropping? I'll just reconnect. Not a problem. Only happens 3 or 4 times a day.
Then there are more subtle ones like IR. Majority of users won't notice. Most of those who do notice, assume it is normal operation and not too disruptive. Fraction of users will report to Apple, friends, other forums. Tiny fraction of those who report it end up in this forum.
Point is, for relatively subtle issues like IR, they are probably severely underreported.