I have the same issue and it's incredibly frustrating. I was able to zoom out completely and scroll back years in few seconds, now I am limited to seeing only 5 photos in one line of the photo grid. Why would anyone remove this feature? It was amazing, flawless, it looked great seeing all your photos as little icons.
I simply cannot comprehend this decision, if it is a decision. If it's a bug, then fine, but fix it soon. But if apple decided to simply limit the view in the gallery, why isn't it optional? Why can't it be just a new setting, why do we all have to view the gallery the same way.
Honestly makes me dissapointed in my device of all sudden. It's like you expect it to do something you've been accustomed to for years and now suddenly the phone is like "can't help you bro, gotta scroll for eternity".
I left a comment at the feedback site that Richard.Taylor reffered to and I hope they will fix this asap.