I did install the trial of BC3 to see the various changes. One thing I will say is that the interface is some what confusing to me. I did install the beta over a month ago, and it is nice to see that there are three panes for the 3-way merge side by side now. It would be nice to get rid of the window at the bottom though.
Why is editing not permitted in every pane though? The fifth feature listed in the original post doesn't seem to apply, since you can only edit in one pane:
I really do like the portable install option though. It hasn't changed a thing in my system, so when my evaluation ends, I can simply delete the folder where the files are.