It's not a totally free ride -- like the Consumer and Release Previews of Windows 8, this is just a trial, and you'll need a Windows ID to access it, as well as either Windows 7 or Windows 8 Release Preview, 3.5GB of hard drive space and a little patience while it downloads.
Not too much patience, however; Microsoft's focus for Office 2013 is most definitely on the cloud, and specifically on saving to its Skydrive service; for the first time you're saving to the cloud by default, with your primary hard drive as a secondary option. Installation comes after a Windows ID login, and you can start using the suite while it downloads… which, as we discovered, can lead to a little instability, but this is just a preview, after all.
Office 2013's cloud-focused approach ties your data to your Windows ID.
Office is still Office -- there's integration with things like Skype and easy YouTube video drop-in, but those who rely on it from day to day won't find too much too confusing -- and predictably everything's been given a bit of Metro paint and polish, right down to the "touch mode" that'll appeal to anyone hanging out for a Windows 8 tablet.
The Office 2013 preview can be installed by signing up at Microsoft's Office Portal here.