I'm really looking forward to this device, and have been putting off getting a Xoom just to hear more about upcoming tablets such as this. But if they add custom UI layers that aren't easy to override (i.e. if they lock down their bootloader and/or I can't find a third party ROM of pure Honeycomb), I'm going to end up getting a Xoom anyway. I really want the stock Honeycomb experience.
Considering you can use the trackpad to move a mouse pointer or hook up a USB mouse I"m guessing it's their custom UI overlay to allow these types of functions to work.
I have to admit, I think my Xoom will be hitting the store shelves again soon. I have a week or so to return it and from what I've seen in the Asus Transformer I'm getting pretty damn excited to see an IPS screen and a quick attaching Keyboard setup like this. IF the tablet alone is $399 for a 16gig version, that a steal imo. Grab a 32gig SD card and with USB support.. this is a no brainer for me. Feels like christmas in April.. or first of June