As to how it works, I'd say so far it's great. The app runs zapping fast, and makes great use of WP7's panorama UI. Panning and scrolling feel utterly smooth. What's more important is that notifications work perfectly in Kik. It's live tile responses well, and the toast notification works exactly like how it should be. Incoming message triggers your ringtone (or viberation), and even wakes up the phone.
To get some more intuitive ideas about it, here is a video tour through the app, credits to WPcentral.