If you're looking forward to the release of Office 2010 next summer (and let's face it, who isn't?!), then you probably already know about the availability of the public beta. If you've tried it, then it would be great if you could share your favourite features in the comments for others to share in your experience.
My personal favourite feature (so far - there are some things that I'm looking forward to trying in Outlook in conjunction with Exchange 2010, when we have that running) is the Backstage view in all the applications. This is the bit that you access via the "Office Button" in Office 2007, which is now accessed through a coloured "File" tab next to the ribbon's default "Home" tab.
What I particularly like about Backstage is that they've brought the live-preview that was such a good addition in Office 2007 to the Print dialogue. You no longer have to look at print settings and print preview separately as they sit side by side. When you make a change to the setting, you see it reflected in the preview immediately. It makes formatting your printouts much more straight forward and will benefit pretty much everyone who uses Office.
I've been using Office 2010 since early on in the Technical Preview stage, before the Beta, but even so I haven't come across all the tweaks in these new versions on the applications, so I was pleased to see that Microsoft Press have released a free ebook "First Look: Microsoft Office 2010". At that price it's a no-brainer to download it!