I thoroughly disliked previous version of Microsoft Office for mobile. I have one HTC Windows Mobile device (the Artemis, if I'm not mistaken - I haven't used it for three years) as well as an old-world PDA, an iPaq (still a powerful little monster). The mobile versions of Office on those devices were pretty horrible.
What Microsoft is showing off for Windows Phone 7, however, is pretty interesting. It follows the minimalistic black-and-white user interface style of the rest of the operating system, and comes packed with online sharing options and integration with other aspects of the mobile device. The videos below show some of it in action (yes, I'm experimenting with the colour options on YouTube - OSNews needs moar unicorns and sunshine).
This stuff could very well be the killer feature for Windows Phone 7 - at least in the business world. I don't think any BlackBerry, Android phone, or iPhone has an Office experience quite like this one.
You can try this stuff out today using the Windows Phone 7 emulator, but most of it is locked away, and you'll need to perform some magic first. The very first emulator image was unlocked within minutes of it being online, and since Microsoft has not done anything whatsoever to prevent it (the method has remained unchanged, despite several new releases), you can pretty much assume Microsoft doesn't care.
Apart from the Office stuff (which was added to the previous release), this latest release also adds the phone and dialler interface, smoother transitions and effects, and of course includes a number of fixes and lower-level changes. The unlocking procedure is detailed at Egnadget, but do note that you'll need the latest .bin file from xda-developers.
Needless to say, this only runs on Windows.