In addition to dealing with a wide range of target audiences, the challenges for a Business Analyst include dealing with a wide range of target purposes. Switching your thinking, your headspace, to meet the type of modelling required for a given purpose can be difficult.
One of the biggest jumps is between business process and system requirements modelling because the goals (and often the audience as well) are so different. The two disciplines require different writing styles, and different tools.
( Long and you probably don't want to look that closely into my head anyway... )