I agree, if you stay off the net you should be fine. We didn't park all of our 8400s when the 8420s came out. A toughbook is a great machine, perfect for updating field hardware. I use a CF53 at work, and it works so well I am considering buying one for the farm.

I want to recommend the SEL-C662 USB - serial adapter. It is a very high quality cable that is well supported by an American company in Pullman, WA. They keep the drivers updated and available on their website and are glad to offer phone support. I am yet to find something wit won't talk to.  Also, it has a switch to alternate between a "null modem" and a "straight cable" so no additional adapter is required.