Linux Distros: Rolling-Release System or Version System?

One thing that has cought my attention the last years, is the so-called "Rolling Release System" Linux distributions.

What this means, is that you don't get to have a new version of your operating system say each 6 months or so, but instead you are always up to date and upgraded. No need for OS upgrades, reinstalls, waiting for new program versions and so forth.

Such distros are Gentoo, Arch Linux, Debian (the Unstable Branch) and others.

So is it any good? What is the downfall? What are the pros and cons?
Lets try to make a small but helpful list:

Advantages:
1) You don't have to wait 6 months (or more in some cases) for your OS to be upgraded to the newest version.
2) You don't have to upgrade to a newer OS version in order to have newer versions of you installed applications.
3) You don't have to reinstall your OS, ever.
4) You are always updated and benefited from new features and bug fixes.
5) You save alot of MBs when downloading upgraded packages, instead of downloading a new version of your OS (which in many cases has many packages of the same version as before).

Disadvantages:
1) It's not as stable as Debian Etch for example, since the time spent for testing new packages is a lot less. In many cases thought, they are more stable than 98% of "version system" distributions.
2) No good for a critical business environment, for the above reason. In this case its better to have a well and throughout tested distro such as Debian Etch.
3) The Version system is easier for software vendors to target. You probably won't have proper support for a game or a commercial application if you're using a rolling release system distro.

However, don't be frightened by the phrase "not as stable as" . Most version-system distros out there are much less stable than Gentoo or Arch and there are only a few which surpass them in terms of stability.

Evaluate your needs and decide which style is better for you. I personally use arch ;)