In essence, all that it is is a CD player that you can also plug your bass into. Yes, it offers some features such as being able to change the playback speed of a song down without changing pitch, and/or changing the pitch without changing the speed of the song. It also allows you to increase or decrease the sound level of typical frequencies used by the bass, as well as offering some basic effects, but that's it. It's just a CD player that you can plug your bass into.
Having said all that, I love mine! I find it useful, but I don't think it's a "cheat" or really makes it a lot easier to learn songs. But it is small, compact, travels well, and is very useful if you're in an environment where you need to practice quietly with headphones. That's why I have mine and it fits the bill perfectly.
Good luck and have fun!
