not all the wi-fi features have been downloaded, AND for the custom stage of the week, it hasn't been a week that brawl has been out. so i'd imagine saturday the feature will be released with the top custom stage (i'll be putting some up, just look for the ones made by XILO.
connection issues:
for some it might be a router setting, but for the rest, random matches will hardly work, the cause? an overflow on the wi-fi network (yes it is possible, nintendo said it themselves.) spectating seems to not use the network as you are just getting a feed on a random match. no interactivity with the battle, so naturally it'll come in clear as a windex'd window.
friend matches will work for now, i've had some good random encounters with 8-bit (those were fun btw.) so yeah thats your wi-fi for today. if something changes, i'll update this quote box
updates
Request for sticky made. 03/18/08 8:30 PM
also i'll list error codes people are getting. this should help with specific problems.