If you, or your significant other, isn't a big fan of ethernet cabling snaking through the house you'll want to hook the Pi up to wi-fi.
However getting wireless connectivity for the Raspberry Pi hasn't been straightforward for some users.
Here is a list of wi-fi adapters that work with the board. If those don't work try plugging the adapter into a powered USB hub, rather than directly into the Pi's USB sockets, which has helped some users.
Others have complained about the complexity of setting up a wireless connection. There are guides for getting wi-fi working on Linux Debian - one of the most common Linux distros for the Pi - here and here. If you're looking to get Bluetooth working with the Pi there's also a list of working USB adapters here.