Recs.
Updated
Beat is a cloud storage music streamer with support for Dropbox, Google Drive, Box and SkyDrive. It's free with ads or you can pay to remove the ads.
Specs
Pros
Pro Straightforward interface
You simply browse through the folders on your Dropbox and select which folders or songs you want to play or add to the playlist.
Play controls along with album art and track title are always available at the bottom of the screen. Tapping on album art or track title will open up the play queue allowing you to adjust it. You can rearrange songs simply by dragging them and remove songs by swiping them away.
A swipe from the left side of the screen gives access to shortcuts that allow you quickly jump between folders and a swipe from the right - to settings.
Pro Can precache next song so you don't have to wait for it to buffer
By default the app will load the next song in queue into cache while the current song is playing so there's no downtime between songs. You can turn off this behaviour in settings if you want to and you can adjust cache limit if you're worried about filling up your device.
Pro Includes a floating widget that allows you to access music controls from anywhere
You can have a small circular widget that floats atop any app you have open. When you tap on the widget it will open music controls.
The floating widget will stick to the side of the screen, but you can change which side and at what heights it will stick to. And you can change the position of the widget at any time simply by dragging it to the desired place.