I am in love with Jaunty.
It has given me the desktop I had been hoping for for a long time now. DRI2 is amazing, KDE4 is finally very polished, 64 bit is working with no problems. This is the most stable "alpha" I have ever seen. I am so pleased that I am using it as my main operating system. As long as I test out the updates in a virtualized environment first, I've had no problems.
There are still a few programs that need to be merged into the repos, like Amarok2 and OOo3, but everything is running quite well.
I feel silly voicing this complaint, but I am really hoping kNetworkManager4 will make it into Jaunty. I have no idea if it will be finished on time, but it will be good to get rid of the last remaining KDE3 components.
EXT4 and Kernel Modesetting would be nice and seem likely to be included, but it would just be icing on the cake. I can't imagine the pace of Open Source development to be as intense next year as it was this year, as far as the deluge of new features. We will certainly see performance and compatibility improvements, but many of the major nagging issues have been resolved.
Does anyone know what improvements are in the works? I am mainly looking forward to the arrival Gallium3D drivers, and I have heard good things about Btrfs. Anything else? Seriously we need to start looking into holographic interfaces or something, I don't know how else to improve.