My department is still using Quark. We have thousands of files spanning a dozen years that are filed away on our server or backed-up.
We studied switching to InDesign, but the time it takes to re-do old templates, was just not efficient enough. Plus, our staff found that InDesign productivity was much slower than Quark.
We studied this objectively, and our staff has had extensive training on InDesign and we’ve taken several projects and switched to InDesign, for our study.
Hands down, the timing to produce work in Quark has proven faster, and more efficient.
One reason for the efficiency is using existing templates, but the other reasons were cumulative, such as faster scroll speed, and screen refresh, less mouse movements to and from the tool palette, etc..
For now, we will continue to use Quark, but will use InDesign for smaller projects.
Eventually, we may need to switch, but we are very pleased with Quark.