[chaosprophet]

The first thing that struck me was the clean, simple interface. The demo is quite nice, and viewing expenses as graphs is quite handy. Since you are aiming at making it extremely simple to use, I suggest you combine all those 4 text boxes (reason, amount, note and date) into one text and use a date time and currency parsing script to get the details.

As to getting users, you could try viral marketing on twitter, facebook and orkut. A large number of Indian users (me included) are migrating from orkut to facebook, so it would be good if you had a facebook app too. Create a facebook fan page or an orkut community and encourage interaction. All this will require a significant amount of time though, so make sure you are willing to spend your weekends on it.