I do use Seamly professionally. For bespoke jeans and pants.
I don’t have experience with the larger, commercial software offerings like Gerber or Optiplex, but I do have extensive experience with Adobe (including drafting patterns in Illustrator).
I started out drafting on paper by hand. Then moved to illustrator. Now I do ALL drafting in Seamly. Then I export to SVG and use Illustrator (or Inkscape) to create a layout that is efficient for my large format printer. And then convert to PDF.
I love the idea of open source software and I try to use it at every opportunity. And Seamly is one of my favorites. With a good active user base, good community. And we have @Douglas doing some great work and making improvements!
Seamly works pretty well for what I do with it. And if I was selling patterns, I believe that I could create a pretty good workflow for drafting in Seamly and then create good layouts for PDF’s in Inkscape.
I would add, is that if your workflow is to draft on paper, then the feature I’ve been waiting for: (Existing SVG file as a background) could be useful. As you could trace over your patterns with Seamly. And then use Seamly to grade and size up or size down based on a of “Individual Measurement” file for different sizes.
What I like about Seamly is it’s a tool that you can adapt your own workflow around. I’ve learned to work with it and use it for what I can (which is a LOT). It has it’s limitations currently, but even the large commercial programs have their limitations as well. Finally, I really find that sometimes a program only SEEMS like it has a limitation, because I may be set in my ways. And sometimes if I just learn to re-evaluate and adapt my workflow I’m able to incorporate a new tool (new program).