Really impressed with the stability of this beta even though there are still stutters when scrolling here and there. But that's about the worst of it.
If this is a sign of things to come then I'm sold.
My only gripe is the useless search screen if you're outside of selected countries. All it throws up are contacts and apps. I really don't need that and there should be a way to toggle the screen off. Maybe apps will be able to "suggest" and "prefetch" info without the need for typing.
This would be a whole lot more useful if it actually showed me favourites from mail which I haven't replied to or read and a better place for widgets. The swipe down should be reserved for only notifications.
Anyway, that's just my take.