Heavy is "wrapper" terms. OpenTK is pretty much a thin wrapper where every function is wrapped like this:
void function(...)
{
glGetErrror(); // Reset error
GL.function(...);
checkErrorAndThrowExceptionIfAny(glGetError());
}
Heavy means that it abstracts stuff away (like window creation under different OS). You just create a new GameWindow object and you have a window open.
In terms of usability, this is awesome
