John Boxall over at Tronixstuff has a detailed review of the differences between the real MAX7219 and the others:
A few people have been asking me of late, and there’s only one way to find out … so over the last month I ordered eight random “MAX7219s” from different suppliers on ebay and will compare them to the real thing using somewhat unscientific methods, then see how they work. The funny thing was that after five weeks only six of the eight arrived – so there’s risk number one: if it doesn’t come from a reputable supplier, it might not come at all. Funny stuff. Anyhow, let’s get started by looking at the differences between the real MAX7219 and the others.