I'm currently using the Live CD version of Kubuntu and quickly noticed that it only has the ubuntu apt repository. Is it compatible with Debian Sid? It has a lot of the programs that I use on it.

No, Kubuntu is not fully compatible with Debian.

Ubuntu/Kubuntu uses different versions of many libraries than Debian when building packages and this makes the resulting binary packages often incompatible, even when the source packages are identical. You can try to install Kubuntu packages on a Debian system (or the other way around) and some packages will work OK while some others won't.

I've got Ubuntu's gparted installed on my Debian Sarge system and it works without any noticeable problems.

I had an horrible experience with Kubuntu. Either you stick to the ubuntu repository (check /etc/apt/sources.list to make sure you are using the "universe" source), or your system will become quite unstable once you try to mix it with pristine Debian-Sid packages. Kaffeine 0.6 was crashing like crazy on my machine, and DVD playback with any application was choppy at best. Kubuntu also does NOT enable DMA by default, so you are probably using your hardware resources at very low speeds

If you are looking for an easy-to-install Debian-Sid, with KDE as default desktop manager, check out Kanotix ( http://www.kanotix.com ); it's a Knoppix clone heavily oriented toward HD installation (even though you can still use it as LiveCD) and hardware recognition (guess what, DMA on by default). It worked like a charm for me in several occasions on different laptops, and the community is nice but smart.