They are very good at solving business problems, but they're not afraid to tell you when there is something that isn't right with your system setup or implementation process - which can often be an overlooked aspect by others in their field! I think this comes from working within various industries / types of businesses for so long; however it doesn't mean we don't learn new things every day about our customers' systems and how/why people do certain operations differently than us (which sometimes leads me into thinking 'this was easy').
It's important to have someone who knows what has been done before because otherwise some aspects will need revisiting. As much as possible make sure all parties involved understand each other well enough to avoid any misunderstandings down-the line if one party thinks another did something wrong without realising why or where it came across like that. For example having multiple applications being.