How many times have you updated a program and then discovered it doesn't work any more, or it's missing something you really liked? For example, the latest version of Screen Mode Widget not only didn't work, it caused the screen timeout to lose settings! And the new Handcent eliminated the "gradient" feature in the bubble settings, which I really like.
BUT- I was able to restore previous versions with MyBackup Pro
(MyBackup Pro v2.3.3 Application for Android | Tools)
In fact, after I did a factory reset, MyBackup Pro let me reinstall all my favorite apps and data. I only had to redo a few settings, and I was back up and running.
This is for non-rooted Droids, and works much like the old Palm Backup Buddy, which was a lifesaver for me.
I don't work for the developer, but I hope he's tuned in!!