A NIC is basically a NIC. If all you do is play games over a network or use it to access the Internet via a cable or DSL modem, an integrated NIC will do just fine. The differences between cards really only shine in high-traffic situations, like a NIC in a server.
Most MBs, however, do not come with a NIC onboard. If you get a MB with one, though, chances are it's a fairly recent chipset and probably OK to use. I've used the same NIC, though, for over three years with no problems or compatibility issues, so they really don't go out of date, either.