The more things you carry with your iPad, the less mobile it becomes. You can get a keyboard that works with it, and USB port devices. When I first got my iPad, I started carrying all sorts of items with it in a bag. Then I got a cover with storage. Now I am just carrying the iPad alone with a protective cover. The whole purpose of the device is to get away from the tons of gadgets that we use with our computers. There are plenty of netbooks and the MacBook Air to meet the demand for a full computer. The iPad is a wonderful device, but it is limited in function by design. The more that is added does nothing for the device.
I'd like to be able to load my iPod nano directly from the iPad (songs I've purchased while browsing at home) w/o having to drag them both over to the laptop (which I usually leave at work). I could then play my new tunes in the car on the way there
The iPad was never intended to be a laptop. If that's what you are after buy one.
In my case, I wanted something that was production capable while being extremely portable and highly intuitive. My use of a USB port would primarily be to dump production files in order to free up the internal memory while on a shoot. I can do that with a single CF card, provided the reader can be connected to the ipad. The USB would be unnecessary if there were stand alone wifi or bluetooth storage devices that could be accessed by the ipad.