Aside from the inherent instability of using a rolling release, I might even recommend using Arch over Ubuntu for a few quick reasons:
A) When you use Ubuntu you just expect things to work and when they don't its been my experience that the documentation may not be quite up to par with other distro's because "everyone expects it to work anyway"
However, when you use Arch, you are expected to set things up on your own so the documentation is quite fantastic and problems that arise are almost always well-documented in advance.
B) Which brings me to my next point: wiki.archlinux.org. What an awesome website. They provide step-by-step instructions for doing nearly everything in Arch. If you are mature enough to read the documentation, you will be pleasantly surprised with Arch.
C) Bleeding Edge. This is a double edge sword. Because Arch is a rolling release you always get the latest and greatest updates for linux, however, unlike Debian where updates are thoroughly tested to death for compatibility, all these new updates will occasionally break things--the main reason you might want to know a little something about linux before using Arch. However, as long as you use your brain and dont update randomly and do a bit of reading before pulling the trigger on your update, you can usually find out the problems people are experiencing ahead of time and then choose to update accordingly.
D) Small and fast. Arch is blindingly fast. There isn't any bloat because you get to decide what you want, when you want, and where you want it. If you think Ubuntu is customizable, then you will have a heart-attack when you move into the Arch scene. I use Arch on my little netbook, 2gb ram, 1.66Ghz Atom and I use my netbook for everything! Generally speaking, I use less than 15% of my RAM for everyday activities--usually far less than 15%. I can program (with Eclipse), compile programs easily, view/edit all Microsoft documents (with OpenOffice, which even my wife prefers now and shes a Windows 7 user!), watch videos in HD, surf the web, basically all the general computing tasks, on my little netbook using Arch and to top it off, I can generally do those things just as fast as an average windows user whose using a computer with twice the power. (Note on Ubuntu: Ubuntu isn't nearly as small and fast, and yes, I refer even to the Ubuntu minimal install).
If you have the patience and are willing to actually read a manual, then Arch Linux just might be the distro that will change your perception of Linux--especially in the netbook world its been fantastic! Just a STRONG REMINDER: to be successful in Arch it takes patience, reading (lots of reading) and dedication, but I promise you when everything finally comes together and you reach that "aha" moment, you wont want to look back.
Disclaimer: (This obviously doesn't include gaming, because, yes, we all know that there are very few software titles that are natively compatible with Linux. If there were, Windows would in a very bad place.
Edited by naval8viation - 2/7/10 at 7:30pm