I think the difficulty level for setting up a two computer network (I'll assume for a home network) could be measured more appropriately if we know the reason for creating such a network. In rare cases people may only want to connect two or more computers to the internet, without a need for sharing files, printers, etc. -- if this is you, then setting up a simple network connecting to the internet through a router is not very hard at all.
However, if you're also hoping to shares files, a printer, or need enhanced security, then I'd highly recommend a network solution product to help make things easy for you.
While some people may disagree with me, spending the $50 to $60 (or so) on a network solution product can and will save you the headache of dealing with network problems later down the road -- problems that can cost you a fortune. Talking to some guy in a Call Center for four hours or having a network technician come to your house probably isn't something you want to deal with. But I guess those who oppose network solutions don't want to take this part into account, the expenses and frustration dealing with connection issues.
At any rate, here are some issues you may run into, if you are using two computers with different operating systems (Windows XP and Vista do not network well together), setting up a home network will quickly become a challenge.
You also need to be careful once you purchase a router because they [occasionally] will assign you a new IP address for connecting to the internet -- problem being, this is coupled with your current IP address given to you through a cable service. If this scenario happens, most users notice major "lag" issues, likely caused by a double NAT home networking environment. These IP addresses are separate from individual computer IP's, so it is important not to confuse the two.
I do work for Pure Networks, the driver behind our Network Magic solution. The best advice I can offer in this situation is to try the free download: http://www.networkmagic.com/product/wireless-networking.php
Without costing you a dime, if it makes things easier, great! You may even want to try the free security scan to help you with your decision: http://www.purenetworks.com/securityscan/
Hopefully this helps a bit! If it means saving you $400 for a network technician, or hours of phone conversations with a cell center dude, then I'm glad I could help.