Office 12 beta 1 is up and running on my Vista 5270 system.
Office 12 is not officially supported in Vista 5270. However, I'm using OneNote 12 to build this tour. Office 12 will undoubtedly be supported in a future build of Vista.
OneNote 12 is significantly enhanced.. and it works great. So well that I've upgraded my three installs of it already. You can see an example of it below - look on the left-hand side to see why I'm enthused about this new release. OneNote 12 makes it considerably easier to have multiple notebooks, and move items back and forth across them.
Office Diagnostics is new and offers a means of checking your Office installation - as well as your hard drives and memory. Should something go repeatedly wrong - and in the beta on XP or Vista it has, this diagnostic tool automaticaly pops up to offer assistance.

Both of these screen images and hundreds of others are part of my "tour" of Vista 5270 (and, now, Office 12). The tour is just that - a tour of images of Vista and Office. You see what I see as I explore more and more of the new features in these new releases. The tour section started in December, and I've enhanced it several times since then as I've explored more of the system.