I like how easy it is to use, that's pretty much all there really are downsides in this system besides maybe being pricey but I honestly don't know if its just because of where we live or what our needs were for pricing etc.
But as far as user friendlyness they have hit home with me! Sometimes you can get so used to something simple, and then when an upgrade comes around sometimes things seem more complicated than before which gets frustrating. This has definitely helped us to be able track multiple projects at once (both current & future) while also providing insight into project budgeting/forecasting issues.