Ooooh new Twitteriness!
My advice on this if you are pushed for time is to slide the slider along to 1 minute. If you actually want to know whats going on read this - http://blog.twitter.com/2010/09/better-twitter.html It looks good, although I use tweetdeck because I have 3 twitter accounts and with tweetdeck I don't have to log in and out.
From the video it seems there will be continuous scrolling through your timeline and a much nicer way to view videos and twitpics froms peoples tweets without leaving twitter. They have created a split screen effect. I also like the look of the tabs across the top of the timeline section, so you can switch to mentions, searches and retweets easily. I wonder how it will change your twitter background image on your profile? Can't wait to have a go!