3D acceleration does not appear to be working on OSE. The checkbox is present, but marking it won't result in VBox.log including the usual information about OpenGL (e.g. "OpenGL Info: Render SPU: GL_VENDOR: blah").
I suspect it has something to do with incomplete handling of the OpenGLEnabled configuration setting. It is checked for, but there seems to be no code to enable it:
$ rgrep OpenGLEnabled src/
src/VBox/Main/VMMDevInterface.cpp: if (!CFGMR3AreValuesValid(pCfgHandle, "Object\0OpenGLEnabled\0crOpenGLEnabled\0"))
src/VBox/Main/VMMDevInterface.cpp: rc = CFGMR3QueryBool(pCfgHandle, "OpenGLEnabled", &fEnabled);