This looks nice but $60/mo seems incredibly pricey when there are also nice, and similar, open source solutions such as http://ricostacruz.com/flatdoc/
Talking from the perspective of a startup person - 60 dollars is less than an hour of dev pay. It seems to me incredibly cheap. I often worry that SaaS startups undercharge and starve themselves out of stability & growth.
We've spent a lot of time putting together our API docs and it's nowhere as nice as this. The service they're providing is valuable to me as a way of solving this problem. I've never met or even heard of anyone working at readme.io btw - saw this on HN for the first time today.
I use ReadMe, and I haven't used flatdoc, so correct me if I make an assumption about what it does.
A huge benefit of ReadMe is the document organization and drafting capabilities. I no longer have a bunch of Dropbox folders that I save Byword Markdown docs to.
I can organize things in a reasonably sane way, and when I am writing new docs (think of docs as a living organism) I can write them in ReadMe and decide when and how to publish them.
It removes a lot of duct tape and glue compared to other solutions I have looked at.
I think if your aim is to crank out a few pages of Markdown and host them on a static site generator, other options might be good for you. ReadMe is definitely first class if you want to create a corpus, and present it beautifully without a bunch of extra steps.
It saves a lot of developer time, you would just have to write the docs in markdown, not have to worry about the layout, hosting or building another app just to manage your docs. IMO it provides a lot of value for money. You could always just use the free plan and then upgrade later. With markdown files, you wouldn't really get locked into the platform.
As far as I see, Readme.io has additional features but everything you've listed is available for free on readthedocs.org, built on Sphinx which is free software.
Why should they not coexist? Some want it for free and some want to pay for e.g. support or additional features.
Last time i watch at RTD it was a plain .md project import from e.g. GitHub only to show a plain documentation.
In Readme.io you can edit/write your docs, have blog function and an integrated discussion plattform (for support your users). If you not need this features, you can use RTD or directly sphinx.
What extra value am I paying for?