This isn't a serious issue, but I do have a delay when turning pages on my iPad 1. It happens sometimes on the iPhone 4s, but typically only if I'm trying to swipe a lot of pages quickly. But it happens often on the iPad. I've noticed that if I turn off inline footnotes (Love that new feature, BTW!) then the pages turn faster, but even with inline footnotes off, I get the loading spinner more often than I'd like.
This is with the ESV, which I have downloaded.