While the app is available for iOS and Android, they don't yet have the same functionality. The Android app offers the ability to stream from an NAS or other computer and listen to internet radio, the iOS app only lets you stream music files from the phone itself or Pandora (the Android version handles both of those features, too).
The Phorus system offers Bluetooth in addition to Play-Fi so users don't have to download the special app to use the speaker if they don't want to, which is a problem visitors to owners of Sonos or other proprietary systems inevitably face. This also means that you can stream audio from any app on your phone -- Spotify, iTunes, Mog, NPR, whatever -- which is useful since Play-Fi (in non-Bluetooth mode) currently only supports Pandora for use in the US. If you're overseas it replays Deezer in Europe, and Asian services are QQMusic and KKBOX.
Compared to the Sonos, the Phorus/Play-Fi app isn't very straightforward when it comes to setup. After firing up the app, you need to hold down the Wi-Fi button on the device for 8 seconds until it beeps and begins to pulse. From there Android finds the speaker and sets it up after asking for your wireless password, while iOS users currently need to perform the extra step of selecting the unit from the available Wi-Fi networks. I found this is the step at which the setup would fail most often -- while the device would give a solid light indicating connection, the Phorus app was no longer able to find it. There were several times when I would select the Music option and the app would tell me "No Play-Fi devices" found, something which would happen even after having just set them up.
Happily, connecting a separate USB-to-Ethernet adapter to the USB port solved some of the connectivity issues -- the system found the unit without having to perform any additional steps. I would recommend this method for anyone having issues, though I still experienced music dropouts.
The first page of the app allows you to select which speakers to play, and clicking on any of them brings you to the sources page, but I found at times it's difficult to navigate back to Now Playing without accidentally quitting the app.
Like the little girl who had the little curl, the performance of the PR1 could either be very, very good or horrid. Given the spottiness of streaming it was difficult to get a real handle on how the unit performed: in the end I had the PR1 connected by a Ethernet-to-USB adapter and was still getting stuttering with MP3s. I tried two different networks, both at home and at work, and I couldn't get the Phorus to connect at home at all. Note that both networks were in close to proximity to other wireless routers, so interference is likely a big factor. If you live away from civilization a little your experience will probably differ.
On a good note, I found that the analog output of the Phorus was close to the Sonos with only a little more vocal detail available with the Sonos. But when it was bad…
With Spoon's "You Got Yr. Cherry Bomb" (FLAC), the PR1 showed a much-reduced stereo image compared to the Sonos Play with the horns and tambourine coming out of the center rather than the extreme left and right as on the recording. My theory is that the Play-Fi system was compressing the song on the fly to squeeze it out of the PR1.
While I originally thought it was a problem with lossless files, I was able to replicate the stuttering, and just plain stopping, for seconds at a time with MP3s as well. The Sonos on the table next to it was running fine with the same file and the same source location. Never mind that the Sonos doesn't support hi-res files, and that Phorus may in the future; I will sacrifice 24-bit quality for better stability and sound any day.
Though the Phorus is less than half the price of the Sonos Connect, its relative instability means it's hard to recommend. Though there's a very good chance Phorus will be able to improve the performance of its gear, it's too unpredictable at present when compared to the rightful leader in this space: Sonos.