We had Pagemaker (forget the version number whatever it was from '88 to '92) on the Mac's in the computer lab at college. Anyone taking classes there was taught how to use it. More advanced classes were given in Quark.
I used both there and then at my first position as a designer. At the time, I liked Pagemaker better then Quark, but then Quark released an update and I started to use it more. Once I learned the way Quark works, and saw how many more companies use it, I got to like it.
We had both Pagemaker and Quark at the print shop I worked at for over 2 years, and we typically pulled all Pagemaker files into Quark since that was better for our needs. We needed to output to large film (30"x40") and Quark allowed us to make the layout pages without any problem.
At the company I work at now, we use Quark, at least at this location. I know that some of the other divisions use both.
Since I tried the beta of Quark 5, I have been thinking about buying a copy for myself. Until now, I have only had access to it at work. I just don't know when I will be able to do this, since I have a few other things that are higher on my priority list at the moment. Things like a larger hard drive for my TiBook, and the Harley.
