A nitpick I had with SDL2 is the inability to render while the window is being resized. There is a rather awkward hack around this on Stack Overflow[1], which involves a callback function that has to call right into your custom rendering routine and "may run in a different thread!"[2].
[1]: http://stackoverflow.com/questions/7106586/keep-window-activ... [2]: https://wiki.libsdl.org/SDL_SetEventFilter