One of the beefs I've had with Netsuite is the lack of documentation on the data schema and how customizing reports can make you want to pull your hair out in clumps.

Making what I would consider to be simple changes many times renders a report useless.  A prime example is when you want to run a sales summary by customer by state.  Pretty basic report for a national sales manager.  However, if you use the wrong "state" field, you could have some really funky results, because there are 3 different state fields you can choose from.

Other reports seem to break when you look at them cross-eyed.  And don't even get me started on the formatting of financial statements.