I think mostly the "lag" people were referring to was simply that those animations were so slow. I certainly found them very annoying, they made the whole UI feel very slow and unresponsive after using my Note 2 with animations turned completely off.
But like you say - they can be turned off completely now. (I didn't mind the parallax thing though, wish they'd given us the choice to turn animations/parallax off separately.)
With the latest update, iOS 7 works very well on my 4S. Actually it has made me completely rediscover that phone, and iPhones in general. I used to quite vehemently defend the "lag free" experience of Android on my Note 2, but now that I am giving my old 4S a serious run again I have to admit that it is overall smoother than my Note 2. (I won't speak for vanilla Android tho, as I have little experience of that.)
I'm even starting to wonder if I really need to satisfy all my touchscreen needs with just a phone. I'm leaning more and more towards having a LTE Nexus 7 for gaming, heavy browsing, reading, general fiddling around with Android - and then an iPhone for calling, notifications, fast shot camera, voice recording, Siri stuff, alarms etc. When I look at the iPhone that way, that smaller screen doesn't feel so archaic and useless anymore. Even the 3,5" screen of my old 4S is well enough for what I need to do with it. Rather, the small size becomes an obvious advantage.
But yeah, I was disappointed with iOS 7 at first, but now I'm getting to like it more and more. It's about not expecting more from it than it is actually trying to be (goes for iPhone in general too).