Even experienced pianists would have trouble sight reading music that uses an excess of ledger lines - i.e. we can't accurately judge what note is intended just

Even experienced pianists would have trouble sight reading music that uses an excess of ledger lines - i.e. we can't accurately judge what note is intended just by estimating its vertical distance from the staff. But notes on the staff (or 3 or fewer ledger lines off) are rarely an issue - it's really just familiarity (I struggle reading off unusual clefs too). Which is why I don't think any sort of piano-roll based notation system is ever going to become the norm for performers, because it essentially does require accurately judging which key to hit, when to hit it and how long to hold it for just by its spatial position on the score.