It helps to as it says clean out key store, content cache, key tokens, etc, all in an attempt to free up system memory so that your BlackBerry runs a bit faster. You can go ahead and enable it if you like. It will only do good, no harm.
Memory Cleaner will clear the active RAM on your BlackBerry not the File Free, any improvement will barely be noticeable.. And after a battery pull the memory cleaner will disable itself is Content Protection is not enabled.
But you are free to enable it as you want.
8830 -> 8330 -> 9550 -> 9650
Just think about how far BlackBerries have come from then till now... And what else is coming.