Running Debian 6 (with a few applications back-ported) on a notebook pushing a decade of use.
Soon I will have a Lemur Ultra. Will play around with Unity, maybe even try Fedora 16. Then most likely I will use Xubuntu 12.04LTS for a solid, stable performing distro, with years of use designed in.
System76 is good components (GNU/Linux friendly) at a good price. If you like Unity (or any Ubuntu distro), you get great fine tuned support. If you like another GNU/Linux distro, you have great hardware components to work with.