Apple have added a Gmail “Archive” feature to the iPhone’s native Mail app. It works in a similar way to “Delete”, in that you swipe the mail you want to archive, but choose to archive instead of delete.
Seeing as Gmail accounts have “unlimited” space for archiving to this seems like a neat addition.
The Mail app will bring significant improvements in iPhone OS 4. You will also be able to manage your email accounts in a unified inbox, switch between inboxes more quickly, organize messages by threads, and even open attachments in third-party apps.
What other minor feature bumps are you hoping will show up in iPhone OS 4.0? Let us know in the comments.