From the Ubuntu 11.04 beta website (my comments are further down below):
Ubuntu Netbook on ARM
In Natty the dedicated Ubuntu Netbook is only used on the preinstalled OMAP3 and OMAP4 armel images. On all other architectures the Ubuntu Netbook edition has been merged with the Ubuntu's Desktop.
The ARM version is the first one to ship our new Unity 2D interface by default, as there are no free 3D drivers available initially in a default installation.
The 2.6.38 kernel for OMAP4 got many driver improvements, most notably the display driver was switched to use the HDMI port by default and auto detect the monitor resolution.
With the Ubuntu 11.04 Beta 1 release, the Ubuntu ARM team is proud to introduce the "Headless" developer image for OMAP3 and OMAP4 hardware.
This image is fully set up for the serial port and contains a minimal command line install.
I am looking forward to the "auto detect the monitor resolution" of the new kernel mentioned above to help Pandaboard newbies get started.
The new Unity 2D interface replaces Gnome. I have not worked with it yet. If drivers etc cause an issue there is always the option of shifting to xfce as the window manager.
The "headless" option also looks like a step in the right direction for a Ubuntu based "minimal" style install upon which advanced users can then install just the components they want. This will help avoid the issues of the past of installing full blown versions of Ubuntu on the Beagleboard and having to struggle through a slow install process of desktop items to only then go an uninstall them all.
All in all it appears Ubuntu is catering for the OMAP based netbook market well in this release and the Beagleboard and Pandaboard communities will share in this bounty.