i use wireless for my laptop, and wired for my desktop
wired is more stable, a bit faster, obviously safer
the only reason i insist on wired for my desktop is because i have my news client running 24/7, so i need it to be as stable and reliable as possible, so i don't come home at night and have to find out that my connection got kicked off 5 minutes after walking out the door, and i lost 8 hours worth of productivity.
wireless is ideal for when you want to move about, most of your downloading is confined to 1-5 connections at the same time, instant messaging, and typical internet browsing. use wired if you're using a high-threaded multi-connection software such as p2p or torrents, or you NEED your connection to be stable 24/7