Nice utility. Few things that I think can improve user experience :
1. User gets no clue about what it is, what to do, how to do until and unless he creates an account. (there should be some kind of demo/trial stuff before logging in).
2. Even after logging in the documentation is very limited.
The thing is that User should know what to do. I understand it's a weekend project but i guess u can use HNers comments to improve it .