Sell it and get an Air 2. Everything is buttery smooth the way iOS 8 is supposed to be. I think a lot of it has to do with all the new internal code. Quick reply, etc is eating up resources. Even music stuttered sometimes on my Air 1. Definitely a case of lack of RAM. on the Air 2 theres plenty to spare.
Nothing to do with RAM, just terrible coding. A lack of RAM would be visible when different apps shut down cause the app you're using is eating up the RAM. Stuttering, lag, frames dropping etc has nothing to do with RAM.