I'm doing that no-Flash-plugin-on-my-Mac thing and couldn't get uploading to work (and I also see a box noting a missing plugin). I "let go to upload," but the window just sat there. Switching to Chrome (which has Flash built in), everything worked fine.

As others have said, just having a standard upload button would work nicely. Same with click-to-copy, there doesn't seem to be a way to get the URL without Flash. Detect Flash, and then add in the "goodies" like that, otherwise the interface is much less usable.

Other than that, when Flash is installed, the interface is nice and easy to use. It's a great start and I look forward to more!