Much like riptide, I think wireless is a very viable solution that many people don't give enough credit to, and that includes for use with desktops.
Ethernet cables are more secure, but it's a non-issue if you know how to manage wireless security. With modern WPA2 encryption the chances of someone hacking into your wireless network are slim to none providing you use a strong password. A hacker will pick the easiest, and many people still use WEP.
Secondly, 100mbit connection speed is only really relevant if you're interested in transferring files between systems. If the network connection is primarily for the Internet, then a 54mbit connection is more than sufficient, and as mentioned, the network speed isn't a limiting factor for most net connections. If it is, then you use wireless N.
Using wireless might be questionable if you only have a single desktop, but it's a better solution than running wires every which way if you have multiple PCs in your home, particularly if one or more of those machines is a laptop. Not to mention the fact that mobile device internet connection is fantastic. My wireless network supports two desktops, a laptop, an iTouch, iPhone, 360 and PS3. If the majority of those were wired (where applicable) the place would be a mess.