USB ports work as advertised. I can charge my iPhone in one port and plug in a wired mouse to the other. I haven't tested data transfer rates, but the gauge of the keyboard's usb wire is pretty thin (standard for a USB keyboard) so I wouldn't imagine the keyboard being a great hub for external hard drives or any kind of high bandwidth data transfer devices.
Multimedia keys work well, volume up | volume down | mute | play/pause | skip work as advertised with no user intervention in regards to the operating system (OSX Lion), although not all of the media keys do something on OSX. There are keys like an envelope, a computer screen, a calculator and a manila folder, and I probably have to do something in OSX to make these keys do something.
Keys are a little squishy. I have to be pretty deliberate about typing or else I miss letters. Multimedia key layout is a little weird, too. Instead of having the Escape key as the upper-left most key, instead there is a "Computer Screen" as the upper-left most key, so feeling for Escape is no longer natural. This is bad for gaming as most games bind Menu to escape, so I actually have to look down to find it instead of just feeling for the top left key.
I'm happy overall. Other keyboards with USB hubs integrated are a lot more expensive. I also like the chicklet key style, keeps things like potato chips from falling behind the keys. If you can remember to be more deliberate when you are typing this keyboard will work for you. If you're already used to a better designed keyboard that doesn't require much force, you'll have to learn to type harder on this thing.