Depends on your needs. One thing is you have to consider the tactile feeling you get off a real keypad. Some jobs requires a numeric keypad to be productive, such as an auditor, accountant, admin etc. Generally it means you often need to key in numbers to the extend you can do it without looking at the keys.
The magic keypad will not cut it, since tactile feeling will help you in your navigation without looking directly at the keys.
Go try out those usb numeric keypad if you like, such as those from belkin etc. Seems like there are numerous reports of these usb keypads working fine, or perhaps just keyboard configuration during first recognition.
