Small improvements to think about
Having just published my longest 'ible so far I generated enough thoughts to write some feedback which may or may not be reasonable.
Embedding content: I see that .stl files appear nicely with ability to preview and interact with them in 3D, that's great. It's also fully possible to embed Youtube videos and they work just fine. What I'm missing however is ability to embed a circuit from 123D circuits - one of the reasons I used the tool for my last 'ible was because I thought it would sure be possible to embed something made with an Autodesk service. Nope. Adding the iframe makes the view appear while I'm writing the step, yet disappears in preview/publish.
Another service I tried to embed was gfycat - they pretty much solve the issue of huge gifs and therefore long load times by some html5 sorcery (I'm not familiar with that). This could save space/traffic of your servers and decrease page load times.
It would also be awesome if uploading an .ino, .txt or any other raw text file would automatically generate a scroll box with the code there maybe even already having the formatting and all. Similarly like .stl generates 3D preview. This would save instructables from another possible wall of text, especially on mobile, because now, when I manually add a scroll box with code in it it still appears like regular text on mobile. As an extra - it would make the work of authors easier as well.
Instructable layout: First of all - I understand and support the idea of having a standardized format of instructables, if this undermines that - forget and forgive me. What I propose is a way to add pictures mid-step to avoid walls of text, since somehow making a new step doesn't always feel appropriate or maybe it's just a personal issue I need to get over? Just say if it is so. At least having a way to remove the "Step #:" when making a new step allowing to have pictures mid-step would help.
Before you mention it - I know that it is possible to add pictures mid-step using html, but that compromises visibility on mobile, so I try to avoid that.
Statistics: After hitting over 50k views in just a few days with my bottle upcycling 'ible I wanted to at least try and replicate that with my other ones. However, when I click the statistics button I have these empty lines next to the visitor count, often the lines with the biggest numbers. While I can guess where most of the views came from it's still massive guesswork and I'm probably wrong in the end anyway. i.e. in that particular case I got over 30k views on my imgur album, my blog post got featured under DIY tag in tumblr and then got some upvotes on reddit as well. I know that your SEO is pretty good from the amount of 'ibles I get as first google results, but fixing statistics has a potential to drive even more traffic for you.
I probably forgot something else along the way, but that's it for now. I hope someone bothers to read this and says what she or he thinks.
Disclaimer: This is meant as feedback and some ideas for improvement as seen from my point of view, not complaints, not even real critique. Read, think and move forward.