Just upgraded to the latest Ubuntu 10.10 beta, so far everything seems to have went smooth, except the Nvidia drivers again, which already failed on the last few dist-upgrades. After the dist-upgrade gdm won't start, but it is easy to fix, make sure nvidia-current is installed and just add the following line to the ServerLayout section in your /etc/X11/xorg.conf:
Option "IgnoreABI" "True"
In terms of new features I haven't noticed much so far, the volume control now includes controls for Rhythmbox, which is a little weird, given that I already have those controls in the Rhythmbox icon right next to it and Firefox has a new set of icons.
Today, when booting up the machine, Ubuntu started to display some three month old identi.ca messages in its notification area, not sure what's up with that.
The new cryptsetup is currently incompatible with the old one from the previous Ubuntu, making encrypted mounts fail without a meaningful error message, one has to add a few additional options to make it work.
Emacs23 with a anti-aliased font is extremely slow when it comes to scrolling.