I'm working with brand new prototype boards and all of the embedded boards I work on have RS232. The reason for this is that it's dirt simple to implement and only needs 3 wires. I only need a few lines of assembly code to initialize it and send or receive a character. It also doesn't care about things like DHCP servers and whatnot, only that you get the pinout and baudrate right. On multiple occasions it was the only way to transfer new images to a board to fix the flash. Of course on some of these boards we use a USB to serial chip on the board and I can crank the baudrate reliably to 10Mbps.
I've also had occasion where I needed to use RS232 to get into my router due to screwing up the network interfaces.