The compiler is slow and is not strong.
The compiler takes much time to compile, even the local compiler is fast sometimes. If you would like to compare online compiler then I have used Sharelatex as well, its MUCH MUCH faster.
ANother thing is that compiler is not able to render document ignoring some small errors such as defined \hbox which is general error and can be ignored to compile the complex mathematical formulas.
I wanted to switch over but this is too much lag to compile and not adjusting to small errors which are prone to happen.
Stay tuned for updated compiler support!
Also, \hbox etc. should be being reported as warnings, so you can still compile your project. If not, please drop us a line at www.overleaf.com/contact with an example. Thanks!
Over leaf is SLOOOOW how to fix?
Please continue to take your time