The ease of use, the ability to customize it for our organization's needs, and the fact that we can quickly get up and running with no training or support required is amazing! I wish there was more customization options in terms of how you want your reports displayed (e.g., customized graphs).
We've been able to create custom dashboards for all types of reporting requirements, from simple monthly financial statements to complex quarterly planning/budgeting processes. It has also allowed us to have quick access to historical data when needed.