Hi Bob.
This v110812 is necessary if you're using s2Member download protection. That said, in the future you'll have other updates that you will need, so it's best that you're ready for them even if you don't need this particular one.
As long as you applied your customizations without changing s2Member files directly, you should be fine. That is, you used hooks to create your own hacks in a separate plugin file, or just changed settings from the WP Admin area. If you did edit files directly, then take note of what the changes were so you can apply them again.
Remember to have Deactivation Safeguards on so you don't lose your settings and info related to s2Member when you update.
WP Admin -> s2Member -> General Options -> Deactivation SafeguardsAnd always make a backup before the update so you can go back to it if something went wrong.
I hope that helps.