I am using Fusion 5, but I have found it to be an excellent tool. It is a more powerful compositor that AE because of the nodes and you can work with 3d well. Has a nice particle system too. AE is better/easier for some motion graphics especially for fancy titles, plus has great plugin support. Ultra Keyer (probably an extra module in DFX 5) is good with green screen footage, providing the green screen is evenly lit and the subject is well lit to separate itself from the screen. The Primatte plugin (an extra purchase) is better for more difficult less than perfect greenscreen shots, plus some other advantages. I only tested it though in DFX 4, not 5.