Plenty of applications where those cr@p USB serial converters don't work.
Tell me about it.
I have a Cisco 8 port managed gigabit switch that decided to corrupt it's OS after a reboot one day, but I can't get in to the console to issue the reset command because I've not managed to find a convertor that can actually send the comms correctly 
Oddly, I find Cisco (and networking kit in general) is fine on usb>serial devices. Its only bit-bashed devices that give grief IME (Cisco, scum of the earth, give me plenty of other grief, just not that
)
I can telnet in to the console and bring up the list of commands available without a problem, however it just won't respond correctly to the delete command when used with a USB > RS232 emu (at least not the ones I've tried).
The same fault occured once before and Cisco sent out a replacement which is still under warranty, I just can't be arsed to spend another £15 posting it back to the Netherlands.
From what I've read on the net it is (or was) a common fault where one file corrupts itself occasionally when you are in the web management making changes, the fix is simply to delete the offending file through the console and it automatically gets rebuilt on the next boot up.
I still have it sat in the box doing absolutely bugger all other than taking up a bit of space, you can have it for free if you have a use for it.