This evening, I upgraded my laptop from Kubuntu 7.10 to 8.04. I followed their recommended upgrade steps, where I used the alternate CD and then updated from that. When I was prompted for conflicts for configuration files, I just selected "use the package mantainer's". I was a little concerned about this, as this was necessary to get sound to work with Ubuntu 7.10, on my laptop.
After booting, everything seems to be working OK, including sound.
The only thing that I have had a problem with so far is that the upgrade upgraded my previous Firefox installation to the 3.0 beta. Many of my plugins are not compatible with 3.0. I know that this will be fixed soon.
Also, I haven't made the switch to KDE 4 yet. I haven't configured it to how I like it, and until I do that, I will stick with GNOME.