Although it’s disappointing that Facebook for iOS is released ahead of it’s Android counterpart I think that’s it’s warranted this time, because of the Facebook integration with iOS scheduled to be released around the corner. They would have had to do a bit of testing to get it ready in time for Apple to finish their part.
So far from using it it feels good. There’s only a few visual changes that I can see, the colour of the Status, Photo and Check In buttons on the news feed (They seem to match their current Android counterpart) and pull to refresh visual is slightly updated amongst small visual cues from opening posts to scrolling. Loading photos is faster, it loads thumbnails first then it loads the image itself which is great because users just keep scrolling quickly until they stop at a photo they want to view. It is also faster, quite a bit faster. There’s non of that
From what I gather, Facebook did the HTML5 way to be lean by having a shell for iOS and Android and the internals all HTML5 to save development costs. This was also used as a way to unify the coding for a lot of the other mobile platforms such as Symbian. But now that they got more funding and massive user outcry over its speed in general they decided to switch back to native.