Summary: I bought the Play:5 after being extremely impressed with the Play:1 and thinking that the 5 will sound better in a larger room. Adding the speaker to the existing network was easy and I like the fact that it has an audio line-in to play music from a phone or tablet directly. The sound is good (I play mostly classical and other orchestral music such as soundtracks) but getting a second Play:1 and pairing them would have been an equally good option for me.
Summary: I bought my second PLAY:5 over the holidays. I have a mix of Sonos devices throughout the house and they all have worked to my great satisfaction. The PLAY:5 is great to fill a room with music. No, it won't please purists - its just one speaker. But the variety of devices available and the quality of sound makes it a great wireless system.
Summary: The SONOS system, generally: We found the SONOS products to be very great-sounding devices, and the wireless aspect worked pretty flawlessly, but you can get similar sounding speakers for much less money. The other issue is, I prefer bluetooth to the SONOS wireless setup at this time. For starters, you don't have issues with certain apps (such as the google cloud) not being supported.
Summary: The Play:5 as a speaker has sound that's quite good enough for me. It fills up a large space (living, dining and hallway) nicely. It also has a line in plug on the back, which is missing (quite disappointing and shame on Sonos for not including it) on the Play:1 and Play:3. A few words about the entire Sonos sytem....
Pros: Great sound. Great control over what plays on which speaker. Many music sources including Spotify Premium (critical for me). Easy to set up. Easy to control if you use your Smartphone for more than phone calls.
Cons: Possible instability of home wifi given the load Sonos puts on it. Not cheap.