mine doesn't do that and doesn't lag. it actually feels faster than iOS 7. but i noticed that a lot of times the same hardware doesn't really behave the same way, at least according to this forum.
Maybe you just don't have an eye for stuff like that, and I'm not saying that's a bad thing. I've used several 1st gen iPad Airs (including my own and many store models, in different stores too) and I notice the same lag and stuttering on all of them, whether it be rotating with the keyboard up, rotating in Spotlight, the pinch home animation, etc. Maybe you got a 1st gen Air with an A8X chip, I don't know. But the lag is definitely there whether we see it or not.
I have personally come to not care about the ugly look of the Reduce Transparency feature. I only notice it in 2 places (the dock background and Notification center) and I'm not around those areas often.