Nothing against it Doug, apart from I could'nt for the life of me get an XP Pro p4 to network with a pIII with Win98.....

Many older games simply would'nt work.
Old uncertified drivers tended to totally screw it up.....
Some games ran slower (although by not very much)
XP's very easy to keep upto date, especially with Cable/ADSL.
My games crazy brother in law uninstalled his (bloody expensive!) XP pro and went back to Win98 S.E. to cure the above Gremlins.
If games arn't your thing, I'd say use XP without a doubt. Otherwise, Win98 all the way.
Anyway, computing without that "Blue screen of death" from time to time just don't seem right to me.... ::)
BTW, I have XP Home. Its still in the wrapper! If CFS3 requires it (doubtful in the extreme!) I'll duly install & use it from then on in. Until something I want to use requires XP, its staying where it is.
As for sharing 56k, I use "Proxy" by AnalogX
http://www.analogx.com/contents/download/network/proxy.htm its free for 2 machines, I'm using it now whilst my "other half" chats to her friends on MSN Messenger.
I can even play Medal of Honor or CFS / CFS2 on-line whilst sharing the connection (V90 Modem, 56k dial up

) and I frequently do!
Hope this is of some use to you friend.

Paul.