Good spotting. Yes it is a micro-usb slot. I can see this device eventually replacing the Curve but given the popularity of the 83xx series this would be a very calculated risk from RIMM
What you will notice the most is the speed at which you can browse the web on a 3G enable device. (And from side by side compares; the Bold is coming in even quicker than the 3G iPhone). At the moment it can be quite frustrating surfing non-mobile friendly sites on your Blackberry. This should all change with the introduction of the Bold.