I'd read a review of the Sonos recently.
I think you'd need to spend more than the projected $800 of the Phillips to achieve a 5.1 system with the Sonos components.
The other advantage of the Phillips is that it's all integrated, with recharging the surrounds accomplished merely by plugging them into the main unit. The unit senses when the satellites are reattached, and goes automatically into simulated surround.
Also I believe the Phillips uses a wireless technology that's a variant of Bluetooth, meaning less interference, whereas the Sonos uses a form of Wifi that is highly stable, but that would put more radiation into the environment.
The Sonos may be more flexible, in that it is modular, but I believe it does need to piggyback on a home wifi system, whereas the Phillips is self contained.
Of course, it also comes down to how it sounds, something we won't know for a few months. Apparently the Phillips is already selling in Europe, but I haven't found any reviews, yet.