These little stereo systems are scary -- any audiophile has a graveyard of Bowers & Wilkins Zeppelin, Oontz speakers, or anything with an iPhone 4 dock. So that's where Sonos products ease our fears: they connect wirelessly (or via an ethernet cable), so there's no danger of its connector being deprecated to the trashheap any time soon.
The thing that is confusing about Sonos is that they are not simply speakers: they are little computer systems, so they handle playlists and multiple units can be synced. It's almost like your iPhone becomes a radio station that your Sonos devices get tuned into, and the ability to have all your devices play the same music at the same time OR to have different playlists going for different rooms is something I have not seen in other systems.
HOWEVER... this is hard to do. Sonos systems have to act as an audio output AND as a playlist manager, but in both use-cases, there are some rough spots that make this recommendation come with a few words of caution. Sometimes if I've been controlling the system with one device (e.g. my iPhone), then another device (e.g. my iPad) can't find the setup. I've had to set up the system more than once. Secondly, having a vintage multi-GB collection of vintage mp3s lurking on my hard-drive means that I have to re-define playlists on the Sonos app, and that's a bit rough sometimes.