You should be afraid. Everyone uses it differently, there are lots of opaque quirks to development and Intuit does wild things like kill their support forums without leaving the old content up for posterity's sake.
There are 2 or 3 different APIs, with verifying levels of support for various features. At times QB will push a release that breaks everything for all your clients and you're left to deal with it.
Not a fun time. edit(spelling)
