What makes you abandon a digitizing tool after the first try?

I built a browser-based digitizing tool with a full editor for tweaking stitch types, angles, density, etc. - basically the tool I wished existed when I got into embroidery. I've had about 50 people sign up, but most try it once and don't come back.

I'm trying to figure out where the experience breaks down. My guesses are:

1. The initial auto-digitize results aren't good enough - so people bounce before even trying to edit
2. The editor is too confusing - the controls are there but maybe not intuitive
3. People don't realize there IS an editor - the landing page has a "try it now" quick preview, and maybe users think that's all it does

A couple questions:

• How good does an auto-first-pass need to be for you to bother refining it?
• When auto-digitizing doesn't nail it, what's the first thing you usually need to fix? (stitch direction? density? missed details? something else?)

Trying to figure out if I need to improve the output quality, simplify the editor, or just make the full tool more obvious. My todo list is still very long, and your feedback would help me prioritize my backlog.

I've posted a link to my app in the comments, any gut reactions welcome!