I have some this about for times.
I use an app called system panel to archive all all my apps to sd card, it lets you archive multiple versions of the same app.
So if you update and don't like the new version or it breaks functionality you can easily revert back to the older version.
The only thing about restoring apps from sd card is that they don't show as installed in the market so if there is an update you won't be notified.