Closest thing to a USB is the camera connection kit. Comes with a USB attachment and sd card reader. You can tweak it to accept other devices, not sure which.
If you don't record video or take pics, or play games on the iPad and already have an iPad 2, I would say its not a needed upgrade. But I got spoiled by the retina display on my phone and I use the iPad everyday so I sold my 2 and got the 3rd gen. I wish they would have upgraded the front facing cam.
I want an LTE iPad but I'm not gonna pay Verizon twice for data, so I'm good with tethering my 3G from my iPhone for now, i can wait for summer/fall to have an LTE iPhone ...