Yup that pt2 MobileBurn video basically confirmed that the amount allocated to app storage is the same as the International Galaxy SII, which is about 2GB. Then a certain amount of the 16GB internal storage is taken up by the system files, leaving the rest as available USB memory.
However, I believe you can move apps around to different storage options (internal USB memory or SD card) once you've installed them. I remember reading that there is a built in app in TouchWiz to do this.