I have the following questions regarding the Fedora Core distribution:

Suppose a person will install Fedora Core 6 and update his system every day via yum. Fedora Core 7 gets released. The person keeps on updating via yum. Will that person, at some early point after the FC7 release, be running FC7?

This one is kind of related to the above: what is the recommended way to update from one release to the next? Why? Is it painless?

In question #1, suppose the person is using FC7 Test 3. Is the answer the same?

How stable is FC7 T3 on x86 on a scale from 0x0 to 0xf?

No, upgrading using YUM in the manner you described will not get you from one version of fedora to another. To upgrade using YUM, you will need to install the fedora-release rpm of the version you want upgrade to. If using FC7 test 3, you will need to do what described above as well as disable the development repositories.

Interesting. But I still do not know the Fedora "idioms", if one can call them such. What are the recommended ways to update?

The recommended way to upgrade is to boot with the new installation media. During the process the installer will find the existing installation and prompt you to upgrade (vs. overwriting).

An alternative, but not officially supported method is as reddazz indicated; manually update the fedora-release, then update the rest of the system.

The downside to an upgrade is that new facilities may not be installed, unless there is a requisite that requires it. After the upgrade, you will need to install the additional function that you want. In addition, during an upgrade packages from third party repositories can cause the upgrade to fail. This is because the repositories are not available during the upgrade process (that may change with Fedora 7).

In any event, an upgrade takes considerably longer than an install. I usually backup user and configuration data, and perform a clean install (fresh partitions). I then restore that backups (configuration data as needed). This way I clean out any old cruft that has accumulated, and I'm sure that all the new functionality is properly installed.

No single methodology will work for every situation; you need to determine which method will work best for you.