The Notes/Domino 8.5 public beta is now available. The forum with all the details (download, release notes, etc.) is at http://www-10.lotus.com/ldd/nd85forum.nsf
I and the rest of the design team monitor that forum, and thus, most of the discussoin will move there; this blog might not be that active for a bit because all the action is taking place over on the feedback forum.
We are planning on doing some usability testing with external users. We have plans to go to customer sites to do usability testing of Notes 8.5, using our "Renovations on the road" approach that Betsy Comstock and the user studies team came up with. As I am sure you all know, Renovations is where Samantha, Ted and Betty work.
We take Renovations on the road by traveling to the customer site, where they have reserved offices or conference rooms for us, and we set up the server (we named it "the big bad wolf") and 3 clients (who are of course named Piggy1, 2 and 3). Then real end users at the customer site come and participate in usability tests. The mail, calendar and contacts are all to do with Renovations topics.
Of course, the ideal thing is to have users install the betas and use it on their own mail, but you admins are very protective of your end users and you don't usually let them install things like "public beta 1" :) so for business end users, we have found that "Renovations on the road" is the next most useful approach.