I recently bought a sonos play 5 and really like it. The bridge is IMO a must if you want to get the most out of the system.
My system works from a iMac which is always on albeit sometimes in sleep mode, it just looks after itself never gets turned of anyway.
The play 5 could work without the bridge just connect it by ethernet cable to your router, it would then create a sonos wireless area to which other devices could connect. However using this method means the unit is stuck near the router.
A bridge creates the sonos network allowing you to place your speaker(play 5 or 3 ) anywhere within range, which will be anywhere in any reasonable sized house.
You then put an app on your phones or tablets and a dashboard on your pc / mac which you can use to control the media.
Although I have a couple of hundred albums in iTunes since getting the sonos I have mostly used it to listen to Spotify and the radio which can be selected through through the App.
Bottom line is it works effortlessly, Mrs W downloaded the app and was surfing spotify within minutes.
Only downside is I now must have more speakers!!