Their player stretches the image (on a PC with web browser) at full-screen. That's gonna be an issue. Hopefully apps show up soon.
(It's better on an iPad (and will run the stream in Mini-mode or whatever they call it), but still skewed. For now, for me, it's worth the $1 a month for the uniform experience. Hopefully apps show up soon.)
(Usefully, though, that direct stream URL will play back just fine in VLC Media Player, which opens a LOT of windows. Good job, WP!)
EDIT: Turns out there are LOTS of ways to skin this particular cat: ChannelPear will set you up to get it into a Roku or Plex (though installing the ChannelPear plug-in might be a little techy), but the VLC route a) seems to be the most global (there's a VLC for Xbox One, didja know that?), b) doesn't require making any new accounts anyplace, and c) allows the most control over aspect ratio for us nitpicky folk who care about that. I am betting there is a simpler Roku method since all you are doing is playing what seems to be a very Roku-friendly stream.)