There's an annoying bug when scrolling in Mail that prevents the first message in a mailbox from being displayed after scrolling down through the messages and then back up to the top. In order to see the first message in the list I need to exit the mailbox and re-enter it again. In some cases, just scrolling down the first time causes that first message to "disappear".
The latest update does not fix this. Since I don't see this being widely reported I'm guessing that this is a 6S-only bug. Has anyone else seen this?