Picked this up since I'm on a college campus and not allowed to run a wireless router in my dorm. Just felt the need to explain why anybody would even need this thing, with the Wii having 802.11G built-in.
Anyway, there's not much to say. Opened it up, hooked it to the back of the Wii, ran the included cable to my network port, then switched my connection to "Wired" from "Wireless" int he Wii Internet options. Done. WiiConnect24 works fine, online games have been working fine, no issues.
The only thing I noticed is that I wasn't able to find the MAC address for the adapter in the menu (I could still find the wireless one). Didn't search too hard, because I just turned off my filter to get it then turned filtering back on with this device added. I'd wager it's probably in there somewhere. I just don't remember it being anywhere that I'd think to look.
Oh, and the ugly beige cord included. I mean, obviously it's just a cheap pack-in, but you'd think they try to find some white or something to match the adapter/Wii. Not a big deal, though, and really I'm just glad they threw in a cord at all.
If, for whatever reason, you need to hook your Wii up the old-fashioned way, this should fit your need perfectly.