I've been using the old school version and picked up the D20 at the Con. Overall it is pretty nice. Really geared for higher level investigators(4th). There are ample handouts for cutting or copying in the rear. The scenarios range from plain vanilla to sardonic. Rather than use existing mythos baddies they create a newer race called the Shykryth that are essentially the luggies from an Azathoth psychic sneeze.
Gun play emphasised over spell craft. At times can seem a bit railroady.
I find it useful with tweaking. Most of the scenarios are useful as one shots.
Worth it? If I had to choose between this or Delta Green/Delta Green Countdown the DG books win. Not as many prepared scenarios, but more food for thought than you can feasibly shake a stick at.
Looking for a start to finish save the world campaign? Try out Nocturnum.
Hope this helps.