A bit of overlap with what I just answered here, and you can grab urls from there, but yep, a Gimp and or Inkscape --> Scribus workflow might be ok. ( Edit: or maybe just sk1 )
Actually done it? Yep. I indeed work with mostly free and open source tools. No complaints :)
In my experience, you often have to use heavily your brain and create your tricks to achieve certain industry demanded requirements when the open source tool hasn't got yet this or that feature. For this reason, the time factor is key to decide. If is needed a very fast, stressful environment, no hassle workflow, very demanding on features, (often is the typical graphic artist job) imho only the best of the best commercial tools would keep it totally safe. Still so, I prefer open source workflows.(generally, not always. but often take the risk. Has the big price of avoiding your boss waste more money. Or keep your money if work as well as a freelance. )