There is a thread with almost the exact same title that was started a few days ago already, but I'll field your question here.
How long after?: Probably soon.
And complaining that the units no longer work correctly? If you don't know what you're doing, which means you shouldn't be jailbreaking in the first place, then it's your fault if it doesn't work correctly.
Otherwise there's not much to mess up, even if something does go wrong, just restore and you're good.