In November 2011, we’ve announced a new catalog layout. For some users, the choice of the catalog might be unclear; “should I use the testing, or the unstable catalog?” (The stable catalog is dead.)
The short answer is: it’s best if you use both testing and unstable.
Let’s consider the alternative: using only one catalog on all machines. If you use unstable (also in production), you’ll keep getting a lot of updates, and chances are that some of them will be broken. On the other hand, if you use only the testing catalog, there will be less churn, but you won’t spot problems in packages while they’re in unstable and you will increase chances of a bad package push to testing.
If you run a site where you have production and development / testing machines, you can use the unstable catalog for the ones that have higher instability tolerance. If anything breaks in unstable, you’ll notice the problem but it won’t be an operational issue for you. If you get back to us with a report, we’ll fix the it, and the bug won’t make it into the testing catalog.