Debian stable is just about the most outdated working Linux system you
can have =). This is great for stability (as the name implies), but
don't expect to see some new software for maybe up to a year or 2.

A /stable/ system in a studio or on stage is a good thing! YMMV.

But outdated packages is not true [any more]. e.g. debian/stable offers
ardour-2.8.11 (the current release), IOhannes is personally pushing Pd
to debian/git and you already find the latest LV2/lilv/SUIL/.. in sid.
need to list more?

The recent stable release was only a couple of months ago, with the freeze six months before that. It will be another 2 years till the next update.

Stable is very stable, which is exactly how it should be, and if what you want is in stable - great. But for example the Pd stuff you mention won't move in to stable until 2013, till then its in sid, and maybe backports to squeeze.