Samsung is rolling out a firmware update for its hot-new Galaxy Note II as we speak. Software build N7100XXALJ1 packs few bug fixes while adding the multi-tasking feature, which was missing in units that went on sale few days/weeks ago.
Using the new capability, you can easily open another app by tapping on the left side of the screen and use it simultaneously. Not a bad way to take advantage of such a large screen, gotta admit.
The update is available via over-the-air or Samsung Kies software. It is suggested that your phone battery is fully charged to have enough juice to complete the process. Moreover, you better connect to a fast Wi-Fi network to speed-up things. Good luck!