The only thing that concerns me is he says the phone has lag. I was under the impression that Nexus phones do not have any lag. I will have to see for myself when mine arrives.
Watching the video closely as he operated the phone, I didn't see any lag. In fact it was running really nice and smooth and I liked the animations. I think he was just assuming that without even using the phone a lot. When he mentioned lag in the scrolling, he didn't even scroll the page, he just held his finger on it and moved the page up and down. Even then I didn't notice any lag.
I have used Iphones and they are exceptionally smooth, and there is nothing like it, but Android has improved greatly. He may have meant how it stutters when the webpage is loading. I didn't noticed it in the video
(because he didn't actually scroll it, like I mentioned) but I've seen it on Android devices. IOS does a great job in that, even though a page has not loaded fully, it will not let you scroll the whole page until it's done loading. What you can scroll is smooth. Android seems to try and let you get all the information as it's happening, therefore it stutters trying to load all the content as is you scroll. It's actually pretty ingenious by Apple to do this and makes the user experience better.