Its the first milestone in our journey to ship this product - beta 1 was released to the Rapid Deployment Programme today. [:D]  This is a significant stage in the development of the products and its great that we are running to schedule nicely.

Having used it now on my live machine for a couple of days it is pretty stable and much more complete than DF4.  It is a bit slower than Office 2003 at the moment but that is to be expected as nothing has been optimised yet.  Features I'm finding I'm using a lot are: Search feature in outlook, tasks in outlook, the floatie is great, filtering in Excel, powerpoint IGX is cool.  I really like the ribbon and have adjusted to it immediately.  I also like the clean, spacious layout of the read mode in Word which I find I am using a lot.  I really love the preview pane in Outlook where you can view attachments as well now - seems to save a lot of time if you just want to have a quick skim of a doc someone emails you.
This is a private beta release for a limited number of customers and partners at this stage.  The beta 2 will be out in the spring and will be widely available. 
If you are using it, post your comments about what features you find yourself relying on now.