If you have FolderEnhancer and plan to upgrade to 4.1 now that the jailbreak is available, then I recommend uninstalling it in Cydia prior to upgrading.

I did not uninstall FolderEnhancer first, and after upgrading to 4.1 I had several problems with folders that did not work correctly, as well as missing icons. And since FolderEnhancer does not work on 4.1, I couldn't even reinstall it to try to fix the problem. Instead, I had to restore from a backup twice before everything finally worked correctly (at least I avoided restoring as a new phone). The problem took a couple of hours to resolve.

Just a heads up.