Hi David.
Congrats on the launch.
As others have said, this is certainly a competitive space, but I imagine there's still room for innovation.
This is a nice technical foundation. If I were you my next step would be to get it in front of real users and begin to understand the unique problem you should be solving. I'd do three things in particular:
1) I'd pursue something like the "customer discovery" process to understand how your product concept maps to real customer needs. (MaxKlein had a lot of good advice on that "below" at http://news.ycombinator.com/item?id=956354)
2) I'd look into usability testing (via paper prototyping or even something as simple as userfly.com) to get a better feel for how users interact with this interface. I imagine there are areas that users might find confusing and ways in which you could streamline the workflow.
3) I'd research the words or language you should be using on the website. For instance, in various places on the site you refer to both "Documents" and "Files". Are they the same thing? You also use terms like "Groups", "Users", "Permissions", etc. Are these terms that resonate with your users? (I don't know that they aren't, I'd just make sure you have the terminology correct.)
I'm sure there are dozens of ways to skin this cat and advantages and disadvantages to each, but one thing that struck me when going through your site is that much of the functionality could be provided pretty much out of the box by other tools. For example, Drupal's free Database File Manager module (http://drupal.org/project/dbfm, demo at http://dbfm.org/, screenshots at http://drupal.org/node/236711#comment-785302) offers most of the same functionality and in places with a little more polish. I've no idea what your framework is (well, from your blog, I'm guessing Ruby), but you might be able to find something that does a lot of the grunt work of storing, serving and moving files for you so that you can focus on the value-add that Docley provides.
For what is is worth, here's a few specific bits of feedback for you:
1) Until you have it ready, I'd drop the "Coming Soon" video image from the homepage. Neither you nor users are getting value from the placeholder and having it there just calls attention to the missing demo.
2) In your grid of benefits ("Save time", "Share safely", "Search documents", etc.), the images are links that don't go anywhere (they just link to "#"), at least they are for me. Also, if these really are meant to be links, I'd make the whole box clickable, not just the images.
3) I'd trim the "Feedback" button out of the screenshots used in your help section (e.g., http://www.docley.com/help/createfolder.html). Personally I think they are distracting and make it harder to follow the breaks between screenshots.
4) I find the tiny document icons a little confusing or misleading. I'd test it with more users than just me, but you might consider adding some text or tweaking the icons a bit. In particular:
a) The icon you're using for "rename this file" suggests "edit" to me. You might want something more like these http://images.google.com/images?q=rename&imgsz=i.
b) The icon you're using for "preview" suggests "search" to me. Maybe just adding a document icon to it might help (e.g., http://images.google.com/images?q=preview&imgsz=i) but personally I still see that as search.
c) I'm not sure what the "Usages" icon is supposed to display. From the icon (a little bar graph) I had expected statistics on the number of times the document has been viewed or something like that (for instance, what bit.ly displays for information on a URL). I guess that is what it is displaying, but it is in a log format that seems inappropriate, especially given the icon you're using. (And I had to look at this a couple of times to realize that you had a download history there, it looks like a commit history to me, something like what I'd expect behind the "Versions" icon.) I'm not sure "usages" is a real word, maybe just "usage" or "use" (although that's easily confused with the verb) or "statistics" would be better?
5) A little bug I noticed: From your help pages (e.g. http://www.docley.com/help/docleyhelp.html) and presumably anywhere you have a subdirectory in the URL your logo link is broken. You probably want to change <a class="logo" href="index.html"> in your header template to <a class="logo" href="/index.html">. On a related note, you might tweak your 404 page to be a little more helpful. It's not currently branded, there's no search or browse suggestions, and there's not even a link back to the homepage. Non technical users might be confused: The only viable option is to click the back button and it seems entirely possible that users may be following a link to your site from an external one so that back takes them off your site entirely.
Good luck and keep iterating!