for practice maybe, but i think, in the long run you would get bored with it because it, if not mistaken, one model can do a particular sound only, like metal would be metal sound, i rather have those guitar to pc connector and use amplitube software, you can get loads of effects, use multiple amps. 
second, this is just my preference. i like to jam along with song blast on pc speaker. so i prefer to have a guitar amp instead. sometimes i connect my amp to laptop (watch movie n such bcause its loud lol), so i just play the song and play guitar on the amp(though the guitar sound wont sound nice when run along with  mp3/laptop)....  using amplug with head phone, i dont think cant really listen to the song. i dont know whether its possible to connect mp3 player or pc into amplug.