This product is so much better value than Microsoft's official product, which will get you 64MB, rather than 4 GB, for the same price! Obviously MS didn't appreciate the competition and has rendered this hardware useless in its latest software release. Thanks MS.
Now if you want to transfer your Rock Band tracks between consoles (for instance if one console fails, which 360's have been known to do in large numbers!), you'll have to buy the official MS memory card and do them one track at a time... Brilliant.