The Control4 WMB will be officially released and should start shipping in June. We have several on order for our clients. I think in regards to the WMB its meant to stream from your ios devices , bluetooth or DLNA, and really meant to be kept in the AV Rack, while the client can stream from the iphone (for example) their music (from Pandora, spotify iHeart Radio to name a few) and I believe your iTunes library. Based on what we have seen on our trainings you can on your iPhone(example) just choose your listening source (Pandora a playlist on iTunes or anything on device) and on the airplay pick the WMB and instantly it connects and begins playing in that zone through the C4. The C4 then brings up that sources metadata. You can then put your phone down in the kitchen, next to bed or wherever your network reaches and let the music stream.
The Sonos is really nice as a source piece as well and does have it embedded in the player, which can be added to the C4 amps and distributed throughout the residence music zones and you only need one EV license per house and not per sonos player. I think what the WMB from C4 adds is the ability to play/stream your iTunes library and playlist directly from your ios devices which a lot of people are asking for with C4.
Then using C4 Amps its easy just to add more zones to listen to the WMB while one is already listening, there is an add zone button where you can add multiple zones on, what's also nice with the C4 Amps is they give you volume feedback on all the zones and you can adjust the volume in any zone to the level you wish.
We have the C4 WMB on order for the office and will be playing with it as soon as it gets in.
Also Gadgetfreaky, you can add your video sources to the Audio matrix, to play through the speaker of rooms that also have TV's.