Well, you know that jailbreaking your iPhone is against apple rules, you know you can't blame them after jailbreaking if anything comes to happen to your device after jailbreaking it. Actually nothing bad about jailbreak and I personally don't know anything bad about it. Reading 2 of your post giving the idea that you fear or doubt something, so fo you to know you can't blame apple jailbreaking your phone will be your own decision and it's legal to jailbreak, but apple doesn't deal with it and of they know you jailbreak your phone you might lose your phone warranty in case you have one. So read about it an know what it is.