Installation with Mythbuntu is very straightforward. Boot from CD and the installation hums along. It will ask you a few questions along the way but you can reconfigure pretty much anything afterwards.
One of the nice things in Mythbuntu is that it lets you configure and install proprietary drivers for Nvidia cards and the like right from within the control center.
Networking has been a bit of a hassle though. Mythbuntu installs the Gnome network manager by default which does not honor the settings in /etc/network/interfaces. I had trouble configuring my system with one ethernet card that is configured via DHCP and the other statically. The workaround was to simply uninstall the Network Manager all together. From that point on the config file was in charge and I was a happy man.
More information about the subject can be found on http://ubuntuforums.org/showthread.php?t=527365and https://help.ubuntu.com/community/NetworkManager.
Mythbuntu 9.04 is out now, but I have not taken the plunge to upgrade. This may happen in a couple months or so.
[EDIT] I have in the meantime taken time to upgrade to 10.04. Everything went pretty smooth. If you are planning on using mythvideo (I heavily do) then you might like to know about the possible pitfalls that come from using the newly introduced storage groups. In short, storage groups allow you to have your videos in separate directories and/or partitions. So you don’t necessarly need to mess with LVM and the like to get one large continuous block device. Another advantage of SG is that you don’t need to mount the video directory in the same location with nfs or samba on a remote frontend. It now essentially works like TV recordings.However storage groups are still a work in progress and switching to storage groups will render iso files non playable. I have also experienced a few other glitches such as audio being extremly slow and/or files simply not playing. I tribute that to the internal player being reworked.