It lags when I am doing a lot at one time. It is like a little computer in your hand, so it can only handle so much with what you got as far as the hardware. But that doesn't mean this phone is a lightweight. It can definitely handle its own. With that said, I have experienced very little lag.
Don't worry man, you will get the phone soon enough, but try not to have a negative attitude towards the phone when getting it. It'll just make you dislike the phone from the start. Enjoy it for what it is, a massively, amazing powerful android device that will give you the freedom of options.