Hey Radim, That would be scalability, extensibility and piece of mind. Our unified editor allows technical writers to use keyboard shortcuts or a toolbar to format text, whereas developers can use Markdown. Slate is amazing, but when you project has 30+ pages, keeping up with links and relations gets hard. Plus does Slate have search with average latency of 2ms? ;)

Finally, it is a fully managed service which will save you many hours of development and maintaining. $39/month is less than what a Silicon Valley engineer is paid in an hour!

Cheers, Z.