tbf m8, I've set up several networks using the tutorial I give above and there have never been any problems with performance or stability. However, we did originally try NetBIOS over TCP/IP (against most websites' better judgement) only to see it fail.
And another thing... if Win98 uses NetBIOS over TCP/IP by default, then why do so many people have problems with networking XP with 98 yet they can network 2K and XP first time without a problem (as you say... 2K also uses NetBIOS over TCP/IP by default). If it is the recommended protocol, then it should work straight away on a clean install... but it never does.
I have never needed to create user accounts on the Win98 box as its basically a home operating system... i.e. security is pretty weak and you can login pretty easily as a guest user. However, the XP operating system is more secure and more often requires the username and password to either be entered on access, or entered into the XP userlist. I repeat... I've never added the user details of the XP box to the 98 box, and I have never needed to... the network always works fine in both directions.
End of the story is... the machines need to access NetBIOS on all the other machines... they can get NetBIOS on the more reliable (outcome from my own testing) IPX/SPX and it works fine - I've never had troubles with it, nor has any other people that have tried it that I know of. My tutorial instructs people how to network successfully (but also without the messing around that playing with the XP network setup disks or NetBIOS over TCP/IP seems to bring).