thr is a high possibility that ur iphone has a new bootrom..making it a subject of tethered jailbreak..which mean, u can jb ur phone, but if u turn it off n back on, then it'll be stuck at da bootscreen n u hv to connect to a pc in order to let it load..so tat is the answer to ur statement..
otherwise, the old phones with older bootrom, they hv no prob after they jb..thr is no side effects except ur phone will run the way u want it to..
n if u ask when the normal jb for ur phone aka known as untethered jb is going to cm out, we dun noe..we just hv to wait...

bro