At this point, USB is becoming a necessity. When i bought my laptop over the summer, there was not a single computer in the store with a serial port.
Requiring the user to buy extra hardware just to acheive baseline functionality from a product is not acceptable. As much as it pains me, i think serial ports are dying. That said, the USB port needs to be IN ADDITION to the serial port. The serial port on the RC is very useful and i have used it for many things othe than just programming and sending data to the computer.