well, we get them for around £120 (well last time i checked) and yes, they are just a protocol convertor. They do come with software but that just sets the box up as a "virtual com port" i.e. trick the pc into thinking whatever is connected to the box is actually connected to the PC.

I think there can be "up to" 90 virtual com ports per PC, but that would be going some I would imagine!

Yes I used a Lantronix UDS100 - the only difference between the 10 and the 100 is whether it is 10Mbits Ethernet or 10/100 Mbits. I got mine from http://www.transtec.co.uk. at about £120

Graham