The new twitter interface is simply reorganized, enabling users to explore trends in an easy way.
You can easily switch accounts on your computer as a mobile phone that does not require a connection or termination of a connection. In other words, if you have multiple accounts, you can quickly switch profiles without logging in or outgoing. Direct messaging and conversation are now in the same window.
The biggest, most noticeable change is that the top navigation bar has been moved to the left sidebar, which contains bookmarks, lists, your profile, and a new explore tab.