This is even better than what it says on the tin. I had some doubt about the cost, but it is well worth it. The online sync is great, come out of the job, a few taps on the iPhone for an existing account - invoice sent.
I used to do invoices in word, and then have to convert to PDF. None of that hassle now - and very easy to send a statement.
How many times have you forgot to send an invoice? And then cant remember what you did.
I have not needed suport, but suggestions have been taken seriously with very quick reply.
Update December 2011, have asked a few questions, and had instant replies, one suggestion incorporated into app. Frequent updates and improvements by developer, many apps should take a leaf out this apps book.