The demo video below shows some core features of the updated platform like the new multi-touch interface, WebKit powered browser, universal search, the latest BlackBerry Messenger client, an integrated RSS reader, and an enhanced media player interface. There's also a new Social Feeds app designed to make social networking easier by integrating information from different services into one coherent stream, and allowing you to update them simultaneously.
Overall, the user interface's graphical elements still look quite outdated compared to the competition, but in the features department the new OS looks promising -- BlackBerry users might finally get a decent browser out of the box. The updated software is expected to debut with the upcoming BlackBerry 9800 (Torch?) presumably by the end of September.