back in 2005, i spent $200 on quickbooks basic to do invoicing for my software business. i had a dedicated windows machine just to run the software, and it was terrible. the interface was confusing, it wouldn't do what i needed it to, and it had a ton of things that i didn't need. worst of all, i was constantly bombarded with messages in the application advertising intuit's other products and services like check printing, payroll, and online data backup. at one point i needed to prepare an estimate, only to get a popup message telling me the $200 version i just bought didn't have that feature, but that i could easily spend more money and upgrade to a better version.
at that point i gave up and made my own web-based billing system (http://corduroysite.com) to do what i needed, and then turned it into a SaaS.