Hi Chris,
I can't look at the link you've posted as I'm currently on a restricted network so this is more in general. If I'd venture a guess that cable is a "standard" USB to serial converter. When connected to the PC and its drivers are installed it'll look to Windows as just another COM-port. The software on the PC and on the PIC will be exactly the same as if you were using a real COM-port.

You say that you don't want to use any converter chips but that's exactly what that sort of cable is - it contains a USB-serial converter (like the FT232 for example). Now, some cables/converters outputs true RS232 levels meaning you'd need a RS232<->TTL level translator chip (like the MAX232) but since you mention USB to TTL I'd think your particular one outputs TTL so it should be OK to connect it directly to the PIC.

As for going "true" USB that's a completely different thing compared to "serial over USB". I haven't yet ventured in the world of USB (I tried once and failed...) so I'm not the right guy to give advise on the subject.

/Henrik.