That said, as long as the site works, I think you should unleash it right now to the public. Don't wait to get it perfect. Release it and carry on working to improve it - using feedback you get from users. Prepare to be very busy though and I would suggest a comprehensive FAQs/Glossary section before you launch. If you don't add one then you might get swamped and not have time to get on with your improvements. Also, I think the yellow highlight is too bright across the top of the homepage.
Finally, to aid comprehension, I suggest that you replace the text in the yellow highlight with: "Take notes (stickies) from any resource including books (both printed and online), videos, podcasts, and more. Share your stickies or keep them private. Learn from others." or similar.
All the best.
But, I have visited your site on different accounts in the past , say about 10 times. Every time I visit your site I:
a) haven't a clue of what your site is about, b) haven't a clue of where to begin to find out what it's about, c) find the design very unpleasant and frustrating.
Could you be more specific about (c)?
You don't need to have import data and export data as links on the front page, especially when I can't even seem to do anything with your site without logging in. Just have "Data import/export" as a bullet point in your feature list; people will get the point.
Speaking of being able to do something with your site without logging in: this is vital. If you want me to make an account, you need to give me a reason to do it. Again, see Thinkature's site, or Adobe's kuler. If you can provide even a subset of the site's functionality to people who aren't logged in, you'll get more signups. Even if you can't do that, it helps if you can explain why the heck I'd want to use your service, like Wufoo does.
This is why a lot of these ycomb reject startups are failing. Their software has obvious flaws and when it is pointed out, they do not work on fixing it.
Your site is fatally flawed. If you wish, mail me at maximusklein at gmail dot com for further discussion. If you don't wish to, start fixing it by explaining to me (and hundreds of other dumbasses like me), what the hell a "resource" is.
To add a note, you first need to add a resource. Then you can click "Add Sticky" under the resource to add a sticky for that resource.
In general, your site is daunting to a new user. Most of the things are not labeled in a way that a person unfamiliar with your terminology and layout conventions could jump right in and start using it. One thing to concentrate on is the names of actions. I see that I can import stickies, but I have no clue why I would want to. Where would they come from in the first place?
A FAQ/Help page would help out some, but it's really confusing from the outset, moreso than it should be for what I think (?) is a relatively simply idea.
This allows you to make backups using export and in case of data loss on the server import your stickies back in.
It also allows you to write a utility to import stickies from some other format.
In the future, I may provide a heuristic import that works with plain text.
http://studystickies.com/#sql%20by%3Aamichail
http://studystickies.com/#computer%20science
http://studystickies.com/#by%3Aamichail
http://studystickies.com/#in%3A0071350047
http://studystickies.com/#in%3A0070527660
http://studystickies.com/#psychology
BTW, the flash demo is a bit outdated but might be worth watching anyway.
For example, I now know what the import/export options do, but there's absolutely no reason for those to be on the front page. I'm not even logged in, so they have zero relevance to my experience. Even for a registered user, they should probably be tucked away under "Advanced" or under some options tab. It's functionality only the techiest of techies would care to use; in general we can trust that you'll keep our data safe and we won't need personal backups. And working on your "heuristic import" is not a good idea either. It's your format, no one else is using it, so just make it simple and parse it in and out.
Your users couldn't care less how cool your code is or how many features you've implemented, just make something useful and make it easy to understand.
People don't worry about exporting/importing until they are significantly invested in the product. And even then...
Also, during pageloads your little "loading" popup seems to have horizontal and vertical scrollbars.