For the casual listener, there's not a huge amount of difference between this and the regular music player, so it does come down to the preference of the user whether they go for the built in app, or this more flexible alternative.
From the directory listing:
- Search all your tunes. Search a track by its full or partial name or by artist.
- Automated playlists. Three types of automated playlists: most frequently played tracks, recent tracks, and search history.
- Fully saved user preferences. No need to re-adjust your settings or select playlists every time you launch the app. Program will do it all for you!
- Selection of music (by albums, genres, artists, and playlists).
- Shuffle and repeat functions.
- Instantly navigate to your currently playing track on the list.
- Quickly navigate through your playlist arranged in alphabetic order.
- Tap and hold a track for full details.
- Play one track only (if you wish).
- Background mode.
From what I can see, Monochrome is passing the information on which track to play to the built in Windows Phone media player. This does mean that you don't have many hoops to jump through to skip tracks and change volume, but it does mean that you need to launch Monochrome (either through a live tile, the start menu, or the launcher in music+video) to use the app for navigation, otherwise you'll end up in the regular Windows Phone music player.
While Monochrome keeps it simple, there's obviously a lot of potential to do something really wild and out there in terms of a music player, but for now Monochrome is a nice alternative that's worth checking out.
You can download the trial version or go for the full priced version from the Windows Store right now.