The streaming music feature works as advertised. Here is the low down.
I have a Linksys WRT54G running the Satori 4.0 firmware running WEP with 128 bits of encryption in B/G mixed mode. The Airport Express is connected in "Bridge Mode" (Extend Existing Network). My PowerBook (500MHz P4) has an Airport card (802.11b), Maryna's iBook (933MHz P4) has an Airport Extreme Card (802.11g).
I can stream music to the Express fine, but the stream suffers interuptions when I background iTunes. Maryna's laptop has no issues streaming music from the disk without interruptions. Note: I have broadband access to the Internet through Cox Cable.
Take it to level two: streaming an Internet Radio channel to the Express AP. Even when iTunes is in the foreground the 802.11b card suffers. I tried various bandwidths, none played for very long before breaking up. The 802.11g card can redirect the Internet Radio channel to the AP Express at 64 kbps while iTunes runs in the background without any interruptions.
The bottom line: if you are running your wireless network in B/G mixed mode, make sure that you are streaming from a computer with an 802.11g card, it will work much better (I could go into a heavy technical discussion of the 802.11g protocol versus 802.11b and why this result makes since, but I'll spare you).
I Can't get the ethernet port to work while in WDS mode at the moment. :(
