I got this not to make a mobile for a baby crib, but to make a hanging, rotating decoration for my wife for Valentine's day. I planned on hanging it from the ceiling fan in the center of our living room with a paper heart while it played love songs, and while it does turn nicely, the included speaker leaves much to be desired. One nice thing about it though is when you connect it to your computer using the included cord, you can delete the music files already on the device and replace them with your own, no special naming of the files required. The included songs sound more like the old midi sounds from years ago that computers used before mp3 files.
But I have no doubt this will do the job of displaying and rotating the decoration for me, I'll just end up playing the songs on a different device. I can't say how long the 2 AA batteries it requires will last as I haven't had it turned on that long so only time will tell about that.