Overleaf.com is really nice too, if you work with others (e.g. on academic papers). The most painless papers I've ever written were with other competent people using LaTeX and overleaf. ShareLatex is good too, I'm not sure if you can autosubmit to journals and preprint servers with it though. That last feature is terrific for academics -- it's how publishing should work, but usually doesn't. I spent the same amount o…
Note that Overleaf.com is proprietary, while ShareLaTeX is completely free software under the AGPL (and self-hostable).
https://www.overleaf.com/help/17-is-overleaf-open-source#.WB...
An open-source business that doesn't survive (cough ReplicaDB cough) isn't necessarily better than a closed-but-extensible one that does. LaTeX itself is, and anything you're working on within Overleaf can be exported as text at any time, so I don't worry so much about lock-in.
The underlying toolchain (LaTeX and packages) is fully OSS, and isn't going anywhere; I have supported the LyX project in the past, and indeed that's how I laid out my dissertation, but in the end I find Overleaf more usable.
I still wish they'd support Markdown, though. Sometimes I just want to run off a quick, properly typeset series of equations and lists/tables without all the boilerplate. I suppose you could make the argument "well, if it was OSS, you could just patch it yourself!", and you wouldn't be wrong. But we use the autosubmit feature a lot, so on balance I've decided I can live with this shortcoming.