Does NOT work with OS X
I bought this based on recommendations that it worked with OS X. It most certainly does not work. Since it was a birthday gift, I was an utter failure.

Good product, but Sibelius Users Beware
I purchased this usb keypad because the newer MacBook Pros no longer have the "hold Function + M/,/. etc. to use a numeric keypad" feature. Other reviews have stated that this keypad does not install directly but you rather have to just select the US ANSI keyboard setting to get it to work.

This method does get the keypad functioning, it may beep at you for a while the first time you use it, but just toggle NumLock and it should stop. However, not all of the keys use keypad key codes. The "Enter" button for example does not send an "Enter" code, but rather a "Return" code. This difference is negligible for people using the keypad only for data entry applications and spreadsheets. However, I use Sibelius, and "Return" on the primary keyboard, and "Enter" on the keypad have two distinct functions. If you need to specify the difference between "Return" and "Enter" on your Mac for applications like Sibelius, then go for the 18-KEY Genovation Micropad 631 USB Numeric Keypad 95/98/W2K/NT/MAC. It installs using the same indirect method as this product, but the keycodes it sends are mostly correct, I was able to get it functioning perfectly with Sibelius without sacrificing any shortcuts.

Nonetheless if you are a Windows user or a Mac user that doesn't need to differentiate between Return and Enter, this is a great product. Three stars for the general feel of the pad and its price, plus one star for the USB hub functionality.

Keypad for Mac
I bought this keypad because another person wrote that it worked fine with his Mac. I have a MacBook Pro, and the keypad doesn't fit seamlessly. I found this suggestion on the Internet:

Press and hold Num Lock key on your numeric keypad first, then connect it. You can then release the key. Press it again if the Num Lock status LED on your numeric keypad isn't on. It should work perfectly at this point.

If this doesn't work, another tip I read on some forum somewhere is to try to press the Num Lock key on your already-connected numeric keypad for more than four seconds.

It does work, but sometimes it takes a little finangling.

Very Convenient
If you own a laptop and do alot of number crunching you have to get this keypad. It will make your computing MUCH MUCH easier. The hook-up is very easy, no installation needed, just plug it in and it is ready to use. No CPA should be without this product. Also the price is great!

Okay
Okay product, i use it all the time... dont really disconnect it from my computer. Good buy