I've got these in Chinese and Japanese. I was really enjoying the Japanese one so got Chinese, too and was disappointed to find that they use the same tunes for both languages. This doesn't help, as the different 'songs' get easily muddled together. Also I found the Chinese tones really hard to distinguish from the background.
I think they're great for one language (maybe less so for Chinese) or possibly two very distinct and different languages, but I wouldn't recommend getting two, at least not until you *really* know the first. Not trying to put anyone off, just useful to know before you buy