My thoughts:
1) The sign up form has a First________Last name field. I thought I would tab from First and land on a hidden Last field because of the gap between the two. Tabbing just moved me down to the next set of fields. If the words First and Last had been closer, I would not have been confused.
2) I cannot type in the date in the New Earning report. It sucks to click 5 times to get to Jan 31, Feb 28 etc.
3) I expected some Q&A about my consulting/tax profile. I file jointly with my wife who is on W2. I expense out things like home-office, cellphone bills etc. I would love to specify these in advance/batch so the tax estimate is more accurate. I don't want to put in every identical phone bill manually.
4) You don't cover Florida for health insurance yet. Understandable for a beta but please don't make this service just for CA/NY.
Even though this is a free tool, I would have gladly paid for it to help alleviate those issues.