Despite the cumbersome nature of the gameplay, it does become familiar as you play on and you will get used to the controls. But really, this is never going to be a game that will have you hooked for hours on end. It's got a good soundtrack and you don't need to carry around a peripheral with you to play it when you're out.
So Rock Band: Unplugged is a decent game for the commute to work or for 15-20 minute bursts every now and then. But if you're looking for anything more than that, you won't find it here.