While I use HERE Maps on my Lumia Windows Phone devices, I don't have it installed on my iOS devices and thus am not sure what the experience was like with it on iOS 7. One benefit of using HERE Maps on iOS was the ability to download maps for offline usage.
Nokia stated you can still go to m.here.com and use their mobile web version. If the experience with iOS 7 is broken then you would think Nokia would update their HERE Maps software and optimize it for iOS 7. Then again, if no one is using HERE Maps on their iPhone then it doesn't make sense for Nokia to waste any more resources developing for the iOS platform.