Solving CAPTCHA with neural networks is not new; this is actually a glorified OCR... What is new, is to do it in JavaScript using the new HTML5 canvas capabilities and pre-calibrated neural network.
John Resig, creator of jQuery, analyzes a very neat piece of GreaseMonkey script which cracks CAPTCHA using new client-side technologies:
"A pretty amazing piece of JavaScript dropped yesterday and it's going to take a little bit to digest it all. It's a GreaseMonkey script, written by 'Shaun Friedle', that automatically solves captchas provided by the site Megaupload. There's a demo online if you wish to give it a spin."

You can read the article on John's website.