I'm surprised to see someone of Bram Cohen's caliber releasing something like this. No one has any business coding security tools unless they've taken time to read forensics whitepapers to look for reasons why their tool won't work. And this tool certainly won't work.
The goal of steganography is to hide the fact that you've transmitted messages. The longer the message, the harder that becomes. This may be suitable for hiding a few bytes, but no useful message is going to be a few bytes, unless it's something like a decryption key (and hiding a decryption key using stego would be crazy). This doesn't solve the problem of "law enforcement wants to know what your decryption keys are, because they've detected you're encrypting data." The whole point of stego is to avoid that scenario.
Anyone who's interested in steganography should start here: http://www.cl.cam.ac.uk/~rja14/Papers/jsac98-limsteg.pdf ... No one who reads that whitepaper and understands its implications would take this tool seriously.
EDIT: To clarify: a message as short as ~50 bytes can often be detected, depending on the stego implementation, because even that is enough to cause statistical anomalies in the covertext which indicates that an encrypted message is hidden in the covertext. So I'm not talking about detecting images or videos sent via stego; just encrypted plaintext messages.