Got home tonight and immediately installed FG-X in my studio. Tested on a variety of sessions from the last 2 years. The main thing I can say to sum it up is I wish I had this plugin years ago.
FG-X has swiftly replaced the following plugins on my master buss:
-  Waves SSL Comp
 
-  Voxengo Elephant
 
- Apogee Dither (included with Cubase 5)
 
- Sonnox Limiter
 
- Sonnox Inflator
 
- etc...
 
Essentially, if you get your mix right, this plugin is all you need on your master buss. A one-stop shop, and it sounds better to me than any combination of the above plugins on any source material I've got - it makes them totally obsolete for me (with the exception of the excellent Waves SSL comp, which I will still use on individual tracks or subgroups, but not likely on my master buss again.)
I know there are a lot of varying opinions out there, I'm just giving mine. The only downside to FG-X is that it's a bit of a CPU hog, even on my quad-core Intel Mac. Such is progress, though - and one thing we can be certain of is that the next generation of plugins will all eat up substantially more CPU power than we've ever seen before.