Most small businesses have no idea what Google Apps is and why they need it. My advice is, let people try this instantly. Your registration asks for a domain. Hacker News folks understand this, but 99% of small business will abandon. I think you are in a great market and I think small business would gladly pay maybe $30-50/year for this or some kind of volume based payments, like, say over 5,000 journal entries is this price, and over 10,000 is this, etc. Remember, anyone can go to Office Max and buy Peachtree for $30. Online, access anywhere, automatically backed up, sharing with my accountant with one click, there are great great opportunities here for web/cloud based accounting. If you appeal to small businesses cheapness this will do great.

I'd eliminate the "Google apps" altogether and just make this work transparently, FWIW.

Also, I am a Peachtree expert, have a CPA requirements from school (I abandoned accounting after my first job interview) and I'd be happy to give you more feedback if that's helpful.