I haven't read everything (yet) but here are a few thoughts :
Setup should somehow tell the user where he can download JSFML (and maybe also how he can build it from the source ?).
Windows says «Alternatively to setFrameLimit, you can use setVerticalSyncEnabled to force vertical synchronization.» but it lack the following warning :
Never use both setVerticalSyncEnabled and setFramerateLimit at the same time! They would badly mix and make things worse.
Same chapter, «Fullscreen and other window settings» paragraph, I think it might mislead some users that DEFAULT is not in the list of flags.
«Our friends at Apple thought of something awesome» nicely put!
Input : nothing to add.
I'll read the other chapters soon.