I like that it's simple to set up, easy for my staff members (both senior management as well) who are newbies in scheduling tasks/projects etc., also very quick once you get used too! It is not customizable enough at this time - which means some of our projects do fall though cracks because they don't have access or visibility into other departments workflows / processes outside those we control directly within MS itself.
We're using Microsoft Project Server & SharePoint so there was no real issue with managing multiple versions until now but if someone had come along earlier then maybe things would be different today? For me personally having all project related information accessible from anywhere via laptop computer has been fantastic since moving back offshore last year!!