What graphics card does it have?
Also is you app doing anything at the moment?
on the addonsExamples/allTestExample at 3360 by 1050 with verticalSync off I get 1700fps
Intel Core2Duo 3.3Ghz Hackintosh with NVIDIA 8800GT
When the app is running you can play with your GLUT preferences by going to openFrameworks (menu) -> preferences.
If it is an ATI card you might have some luck downloading the ATI control panel which lets you play with some performance settings. http://aaron.gy/stuff/atidisplays
Also does it make a difference if you call
ofSetWindowShape(3360, 1050); in testApp::setup
and just ofSetupOpenGL( 640, 480, OF_WINDOW); in main.cpp