I've used Dataman to monitor my data usage the last few months on my iPhone 5s and it has always nearly counted like AT&T's meter. However, with iOS8 it is showing i've used 1.57gb for the month and AT&T's meter is showing i've used 1.8gb. I've also been a victim of the slow wifi. Maybe Dataman has a bug -- i'll reset my iOS usage stats next cycle and see how my phone counts the data usage. Is anyone else running into this problem?