Excel: The new version of Excel will allow you to create sparkline charts, tiny graphs that fit within a cell and summarize the data in the preceding cells. Another addition is slicers. These are essentially macro buttons that allow you to filter the data in a pivot table with one click.
I hope that both new features will be better explained in the final version of Excel because I couldn't manage to make either work in my preview version. Neither is included in the preview versions help file and both were greyed out on my ribbon bar.
Outlook: Microsoft seems to have made an effort to make Outlook fit in more, making it more like the rest of Office by giving it the full Ribbon interface and more like webmail services like Gmail by showing threaded conversations.
In Office 2007, Outlook was inexplicably left out of the Ribbon makeover. While Microsoft developers at the time had a rationale, it seemed to me like they had just ran out of time to rework the mail clients interface. Now it gets the full treatment and whether you love the Ribbon or hate it, at least the suite is now consistent.
If you're on a long string of replies to a single email, Outlook will now pull all of those messages together so you can see them all at once. If you get tired of the conversation, you can click to ignore it, automatically deleting the messages and any future replies. (The feature is similar to muting a conversation in Gmail.)
Quick Steps is a promising new feature that's confusingly implemented in the preview version. The idea is that you can easily create a macro that lets you do the same thing with various messages with one click. For instance, I created a Quick Step that automatically forwarded a message with the "WTF?:" inserted before the subject.
But that Quick Step only showed up in the drafts folder, where I created it and not in my inbox. In fact, the menu for Quick Steps didn't appear at all in my inbox, only when I opened a specific message - and even then the presentation of this feature was entirely different than it was in my drafts folder.