I have a Tascam GB10, that I use for playalongs and I think it's great. It's small, batteries last for ages (an adapter is available separately), and it's simple. Plug the bass in, plug the headphones in, and go. You just connect it to the PC to upload or remove MP3 files. Probably the most useful feature is the ability to change the pitch of songs at the touch of a button without changing the speed, it's great not having to retune for different songs. Conversely, you can slow a song down without changing the pitch, and you can loop sections of songs too. If I'm being picky, the sound quality isn't brilliant, but it's decent. It also has a few effects (which I've never used so can't rate), a metronome, a tuner and It'll do simple overdubs. It's a great little tool IMO, I've had my money's worth out of it.