I've been told before that this advice isn't appropriate for anyone who isn't a Debian developer. Things can break and testing may not get important security patches until a while after unstable and stable.
In my experience, the "here be dragons" description of testing/unstable is way overstated... they're both very reliable. If you install apt-listbugs and `apt-mark hold` anything with bugs that sound scary, you'll be fine.
It seems like a lot of people try Debian stable (perhaps thinking of it as an upgrade path from Ubuntu), are surprised by the ancient software packages, and then look elsewhere. Debian might want to consider changing the recommendations they make for new users. Instead of stable / testing / unstable, they could be server / workstation / testing.
> Instead of stable / testing / unstable, they could be server / workstation / testing.
I would love to see something like that, but I think it would need significant changes to Testing to make it usable for the masses. Some years ago there was some work towards that direction with Constantly Usable Testing, which explains some of the challenges: https://old.lwn.net/Articles/406301/
Debian is great in general but the wonkyness surrounding the freeze period gave me the impression that Debian Testing really is something that should only be used if you are interested in helping Debian produce the next Debian Stable release. Some packages don't get timely updates and are only updated close to the freeze period, in preparation for the next stable release. And during the freeze period itself everything is super awkward because preparing the next stable release takes priority over keeping Debian Testing usable.