Like you I haven't paid for software myself in nearly a decade. I have either used Open Source or had software bought for me.
There are many more arguments for using open source over commercial, for example in general open source code is cleaner and better written than commercial as it acts as a kind of CV.
The only 2 places I would possibly be comfortable with commercial software is for a single client proprietary solution in which you are often protecting the company's IP and computer games (and even then I find some open source games better than the commercial alternatives).
I am really disappointed by Zend Studio for example. Judging by last time I used it (about a year ago) it is written in Java and quite often doesn't conform the OS GUI standards (especially Mac OSX). It may sound like a minor niggle but it is a major factor for me, I like my apps to behave the same way, hence why I use Gnome as it has a standards document for just such a thing.
Ill leave you with one thought, have you ever met a software sales droid with scruples?