When apple warns it's users not to jailbreak the iphone, they want you to be aware that it will void the warranty. Under these circumstances, it is only normal to avoid any app that allows you something that can void the warranty and the benefits of OEM support.
The first time I became familiar with this app popular with young people; I too was interested about the benefits of using an apple phone after jailbreak. It is supposed to help you customize the phone just as easily as a rooted Android phone.
But my question is, at what cost?
It is a few years back, but I still remember the day I recieved a call when I was working for a helpline for 3G phones. The young woman was crying because she had bricked her iphone after trying to use this jailbreak app. I tried to calm her down so that I could try and help her find a solution on her own although the only official answer I was allowed was this. I had to say that any issue related to iPhone after jailbreak app was used is not supported by Apple and its helpline. This is just one example from multiple such calls I recieved in 3 years working there. And all of these people were not aware of the pitfalls of using such an app.
If you stop to think about it, i'm sure that you cannot disagree with my dislike for such an app.
