Now that all the jailbreaking tools use the same exploit
it looks like finding the right one that won't break your device is no longer an issue - they all break your device!
The reasons why most hackers only use know security holes are either trying to be one step ahead of Apple, so the hole doesn't get patched on the next iOS release or simply keep the secret that gets them your credit card number.
So with the new jailbreak out everybody should be happy right? With all the unlocked features like working bluetooth transfers, mass storage mode, Symbian/MeeGo visual style (real) multitasking, even a half backed Flash version taken from Android and hundreds of other tricks they should be!
But unfortunately for most of the users the cellular data connection. and FaceTime are broken. There have been reports that jailbreaking your iOS 4.1 device with one of the latest jailbreaks (Greenpois0n, Limera1n, or PwnageTool) can result in breaking FaceTime and getting no cellular data connection. Not exactly what you expected when you wanted those common sense features any other manufacturer offers, now is it?
Thankfully, there is already a fix that well, seems to work for most users. Apparently the issue has to do with some low-level SMS communication and a reset of the phone's carrier bundle, things that can only be fixed by downloading yet another app from Cydia and tinkering into the phone's settings.