The ease of use was one thing that I enjoyed best about this program! It's very user friendly with all those features you need in an office suite as well as some extra ones too (like scheduling).
However it is not easy for beginners who are used to other programs like MS Word or Excel which would require less training time than what they'd get from DDOI. For me personally - since my work requires writing documents almost everyday so having everything right there at hand has been great for productivity level gains while keeping costs low. We have reduced our paper usage by over 80% just through using ddoOffice only.