Ken. Good news that the USB interface is at last shipping!!
PF...The poor old 1747-PIC was a never the most elegant of things. Remember it was designed in the late 1980's and predates laptops PC's by a 3 or 4 years.
The PIC is powered from the serial port RS232 lines, which in the early days of desktop PC's were usually a healthy +/-12v or so, as per the RS232 spec.
As time went on it became increasingly rare for ANY PC serial port to support the original 12v. The better laptops of the 90's would do +/=5v and the PIC would light up ok, but barely.
Most modern laptops barely poke out 3.3 v and the PIC only works erratically at that voltage....if at all.
Plus of course Windows 2000 and XP demanded an entirely new certified driver to run DH-485 out the serial port, and this left users of the PIC driver unsupported in Win2k for about six or nine months. The latest versions of Linx ship with it, but it still catches the odd folk out with earlier versions.
Plus as Ken mentions, the device driver runs as a Windows kernel device, and usually needs a re-boot to swap the sucker out.
The PCMCIA standard was meant to be the way forward, and has provided a good solid solution in the form of the 1784-PCMK, PCD and PCC cards.
These cards work well. (I own and use all three.)
However the USB port is the latest fashion to take over the PC world, and it is good to see a decent interface for it at last.