Alarm
It's quite laughable, since iOS 4 or 5, it seems that (virtually) any vaguely major release of the product is unable to cope with alarms (and/or daylight saving time change). We had the don't ring, ring an hour earlier, an hour late, 12 hours late, only when repeated, only on weekdays variations.
So seriously, especially now they entered the watch market (even if the wrist appendage is probably not used to read time), shouldn't Apple be on the market to buy an alarm software that works for a few £100m?