Pros: Quick, easy, and works like a charm.
Cons: I've been trying to think of one. I can't.

Although it's rare these days to buy a computer lacking a built-in ethernet card, we had an older one lying around that we wanted on the network and it lacked a card.

My wife picked up this card at OfficeDepot along with a Linksys 5-port workgroup switch for $29.99 on a buy-one get one free deal.

I installed it in the PC, and I used the supplied CD-ROM to set it up. I think I had to click the mouse 4 times or less in order to complete the installation. Done.