A few thoughts: don't make me sign up to try out the service. I don't want to leave a trail of dead user accounts around the web because I decided to try out your service. Most of the time, if I can't see a video demo immediately or actually access a demo version of the site I just move on.

A lot of your copy on the front page is feature-driven rather than user/problem driven. From looking at the landing page - I'm not entirely sure what problem/pain this product is meant to solve. I get the use-cases, but they aren't exactly problems for me at the moment so you haven't really sold me to try it out. There's probably a use case that would appeal to me but you haven't found it yet.

Also - the flexibility of your system means that you need to let me know how I should use it. I have no idea how I should start - there's no defined structure and I'm not entirely sure what the best way to get value from it would be (e.g. what should my lists be called, when should I create a new list versus use an old list).

It's very similar to Google Wave - in that it presents a bunch of tools to use but no indication on the best way to use them. This is not good from a user experience perspective (I am left feeling like I'm not using it correctly or in the best fashion - not a positive experience).

There's also no user feedback form/email on the landing page - I'd rather send feedback via email.