It looks like a nicely designed homepage that gets your point across well.

I clicked on the "Switch from Delicious?" button expecting to be able to authenticate with delicious and get going straight away. Instead I got a not terribly well presented list of reasons why I might choose to switch. At the very least there should be a clear call to action at the bottom of that list.

For sign-up is the CAPTCHA really necessary? If I understand your service correctly there is relatively little advantage to be gained by signing up multiple spam accounts and the presence of the CAPTCHA will reduce legitimate sign-ups.